The original Warcraft III game was already quite an excellently designed strategy game during its time, if its official game modes are to be examined. In terms of enabling users to make content of their own, Reign of Chaos already offered quite a very good scenario editor that allows the player to create adventures that the editing tools of other strategy games just could not offer.
As an expansion made by Blizzard, Frozen Throne does the usual things expected of such a Blizzard product: it adds refinements and some new but minor features to the main game modes. However, its most important contribution is the sheer upgrade that it provides to the scenario editor that came together with Reign of Chaos. This upgrade allows the user to practically craft maps that have gameplay that is very, very different from that of the main game mode.
Of course, the expansion also comes with a narrative continuation of the Warcraft saga. The story picks up where Reign of Chaos has left off; the fallen Arthras and his undead host are laying waste to what was once Lordaeron, though this relatively uneventful start (compared to the levels of epic melodrama that plots in Warcraft tend to go to) eventually escalates to the usual high-fantasy story about the world being threatened yet again.
However, Blizzard has included plot elements to make the story less of a cookie-cutter. The characters in the Frozen Throne storyline do develop in terms of personality and goals; these developments also play very strong roles in how the story turns out, i.e. Blizzard does not resort to introducing too many new villains or heroes as a deux ex machina to bridge over gaps in the story.
(That would only be true for this game, of course – not necessarily so for Blizzard's next ones.)
The Frozen Throne campaign is also used to showcase the expansions to the map editor's features. There are scenarios where the player takes control of custom-made factions that play differently from the official ones. It is also used to show that Blizzard acknowledges and embraces the gameplay ideas that users have conceived using the Warcraft III game editor, such as one scenario in the campaign where the gameplay is akin to a tower defense game (though the scenario does seem very out of place with the rest of the associated campaign).
In addition to the Frozen Throne official campaign, this expansion also includes another one that concerns the Horde's attempts to strengthen their hold on the more desolate regions of Kalimdor amid the turmoil from the exodus from Lordaeron. Blizzard intends to use this campaign to showcase another feature of Warcraft III's enhanced editor, which is its ability to string together maps into an RPG-like experience, with Hero mechanics that are different from those in the other official game mode.
This is a very impressive feature, though this official campaign also shows how the mechanic of heroes and their advancement systems can be brought to imbalanced (but very entertaining) new heights.
The campaigns may provide the entertainment that a fan of Blizzard's sagas wants, but they do leave a lot of unanswered questions (which would later be answered through the World of Warcraft MMO).
Of course, if a player is looking for how the official game mode has been improved, Blizzard does provide some new things and changes to fill in the strategic gaps in the designs of the game's four official factions.
The Alliance gains the Spell Breakers, which are better at countering enemy magic than the Priests are (thus freeing the latter up for healing roles, though they retain their ability to cast an area-effect Dispel). Then, there are the Dragon Hawkriders, which give the Alliance hard-counters against enemy defensive buildings and air units.
Perhaps the most impressive improvement is the changes in the mechanical units that the Alliance have - and which were rather impractical to use in Reign of Chaos.
The Steam Tank has been superseded by the Siege Engine. While it has been made bigger with a bigger hitbox, its costs have been reduced. Its most important change is its Barrage upgrade option, which turns it into an anti-air battery that can clear the skies of flocks of weak aerial units, making convoys supported by Siege Engines very difficult to harass.
The Flying Machine now has access to the Flak Cannon upgrade, which also makes it devastating against flocks of weak aerial units.
Possibly with a theme of Dwarven ingenuity, the Mortar Team has access to a new upgrade too, which makes them effective against most flesh-and-blood enemies as they are against enemy buildings.
The Alliance also gains the Arcane Tower, which is an upgrade to the Scout Tower. While the Arcane Tower does less damage than the other upgrades, it does have the ability to detect stealth units and also an ability that counters spell-casters that are attempting to overwhelm Alliance defenses with magic. This tower does require more micromanagement to use though.
The Horde gains the Troll Batrider, whose use as anti-building raiders only becomes apparent after purchasing their Liquid Fire upgrade.
The Spirit Walker gives the Horde a much needed area-effect anti-magic capability. However, its other abilities may cause some gameplay imbalance, as it increases the durability of the Horde's army as well as its Tauren units.
The Troll Headhunter can now be upgraded to the Troll Berserker, benefiting from not only better stats but the tactically useful Berserk power.
The Horde can now alter the armor type of Burrows and Towers, switching them over to Fortified with the Reinforced Defenses upgrade, which makes them less susceptible to raids by fast units that do not have siege capabilities. Speaking of siege capabilities, the unit formerly known as the Catapult and now called the Demolisher can be upgraded to cause additional burning damage to buildings, giving it qualities useful for raids too.
The Scourge gains the Obsidian Statues, which gives the Scourge's undead army the sustenance that it needs when it ventures out of blighted terrain. The Statues can also morph into Destroyers, which give the Scourge area-effect anti-magic capabilities, as well as a rather powerful aerial unit that is faster than the Frost Wyrm and more durable than the Gargoyles.
The Scourge's need to spread the Blight meant that they can barely keep the location of their bases a secret, and will have little choice but to set up defenses for an attack that will more than likely happen. The new Nerubian Tower upgrade for the Ziggurat helps in defense efforts by slowing down attackers with its cold-based attacks.
The Meat Wagon now has access to an upgrade that gives it the ability to generate corpses automatically, much like how the Crypt can. The additional corpses do help make the corpse-related powers of certain Scourge units a lot more competitive, though it may result in some gameplay imbalances if other players cannot obtain the necessary counters quickly enough, especially if the Scourge player has purchased the new Skeletal Mastery upgrade for the Necromancers, which let them raise skeletal mages together with warriors.
The Crypt Fiends gain the ability to burrow, effectively becoming a stealth unit and also gaining greater regeneration rates, thus allowing the Crypt Fiends to keep up with other Scourge units in recuperating after a battle, or to act as sentries around the map.
The Abomination can also Cannibalize now, giving the Scourge player the solution that he/she/it needs to have the Abominations keep up with the Ghouls.
In Reign of Chaos, the Night Elves lacked a reliable tank-like unit; there are the Druids of the Claw and their were-bear forms, but the shape-shifting happens to take away their very useful spells. The solution for this is the Mountain Giants, who conveniently enter the canon of Warcraft as allies of the Night Elves.
To protect the often high-value but fragile units of the Night Elves, the Mountain Giants can execute their Taunt ability, which hijacks the targeting AI scripts of nearby enemy units to force them to attack the much harder Mountain Giants instead. This won't work against human players who can see this happening, but they do mess up said players' micromanagement every time Taunt is used.
However, their other ability may cause some balance issues. This allows them to rip up any nearby object that has been designated as a source of lumber into a makeshift-club that increases the range of their melee attack and changing their weapon type into Siege, giving the Night Elves a close-combat solution for attacks on enemy bases - something that they had previously lacked.
The Faerie Dragons appear to give the Night Elves dedicated area-effect anti-magic units, though they are rather fragile if the player cannot micro-manage their skills efficiently. Considering that other Night Elf units also have powers that will demand the player's attention, making use of these new units alongside them may require some serious actions-per-minute capability.
The Night Elves' Moon Wells have been rather instrumental in helping the Night Elf mount a defense of bases, or even an assault, if the player is daring enough to set up forward bases. The new Well Springs upgrade improves the capabilities of the Moon Wells some more, further encouraging such tactics.
In Reign of Chaos, the Druids' animal forms do not allow the use of their very useful spells, which discourage the use of these forms. There are now new upgrades that allow them to use at least one of their spells when they are in animal form, though this improvement should have been available by default to make them more utilitarian.
Each faction also obtains a new Hero that gives it new tactical possibilities, or to address complaints about strategic drawbacks that their armies have.
The Humans gain the Blood Mage, which is the fiery counter-part of the Archmage.
Unlike the Archmage, whose spells require quite a lot of thought and deliberation to make full use of, the Blood Mage's spells can be brought to bear very quickly.
Flamestrike is an almost immediate area-effect attack that also doubles as an area-denial weapon, while Banish can be used against troublesome combat-oriented enemies, namely melee-heavy Heroes, to take them out of the battle temporarily, as well as render them more vulnerable to magic-based attacks. Siphon Mana is another handy spell to stymie enemies with magical powers, especially magic-oriented Heroes. All these abilities make the the Blood Mage very, very utilitarian.
His ultimate spell conjures a powerful summoned creature that can fly and immolate nearby enemies. It can turn into an egg and resurrect within 10 seconds, though it wouldn't be much help against human players, who will more than likely send something its way to crack its fragile form.
Although the Phoenix is technically a summoned unit, it has passive abilities that protect it from units with powers that are devastating against summoned units. This can result in some gameplay imbalance, as the Phoenix can be rather difficult to take down.
The Horde gains the Shadow Hunter, which gives the Horde army Hero-sourced healing (which they lacked in Reign of Chaos); curiously, the coding for his healing power appears to have been derived from that for the Farseer's Chain Lightning ability.
In addition, the Shadow Hunter can set down mini-turrets (called Serpent Wards, though they are functionally mini-turrets) to help the defense of territories. He can also Hex enemies, namely other Heroes, to take them out of battle temporarily. Hex is perhaps the most useful Hero-disabling spell, as unlike the others, it can negate the bonuses of equipped gear as long as it is in place.
Finally his ultimate power turns nearby friendly units completely invulnerable, but not himself. This can make him a prime target almost immediately, but being a Hero, he can use items to grant himself protection, possibly creating balance issues.
The Scourge gains the Crypt Lord, which serves as a tank. It does not have any abilities that augment the Scourge's army (unlike the other Heroes), but this also means that he is less of a target priority. However, he has abilities that allow him to take on a small army on his army, making him devastating against scouting or raiding parties. More importantly, as a hero, he still has the ability to use items, which enemies cannot so easily assume that he has.
He also has an ability that spawns Carrion Beetles, which unlike most summoned units, do not have the Summoned Unit property and can be used as scouts and sentries.
In Reign of Chaos, the Night Elves lack a Hero that has powers of mobility or durability that can be utilized for the purposes of scouting or defeating neutral creatures. They now have access to the Warden, who may not be very tough, but has abilities that allow her to dance around enemies and damage large groups of enemies, or target specific enemies (namely other Heroes) and hobble them.
Finally, her ultimate power summons a strong ghostly spirit which can in turn raise other ghostly units, albeit the latter are invulnerable. This is not unlike the Death Knight's ultimate power, though it requires more micromanagement. However, the main summoned unit does provide some extra firepower.
To further augment the mechanic of Heroes, every faction can now build a shop rather early on in a game that can be used to purchase items for Heroes' use; only said faction's Heroes can use them. At first, their selection is rather basic, e.g. the usual early-game essentials such as healing and mana potions, but as the player upgrades his/her town center building, they gain more items for sale.
This mechanic helps alleviate a problem in Reign of Chaos, which was that players can anticipate that their rivals may attempt to reach neutral-aligned shops in the map to purchase some early-game supplies; this in turn can result in some silly fights that occur right outside them with players being able to purchase items off them as long as they can get Heroes into shop-browsing and back into battle in alternating manners.
If there is a complaint with this feature of faction-specific shops, it would be a minor one: the Night Elves' shop appears to be slightly more utilitarian, as like other Ancients, it can uproot to defend itself from enemies. (Fortunately, Night Elf heroes may not peruse its goods while it is walking around.)
Certain units can now also be upgraded with Backpacks, which allow them to ferry around certain low-level items, such as Healing and Mana potions for use by Heroes if the player would rather want them to be lugging around more sophisticated gear. However, the player may have to perform some micromanagement to switch gear out from Heroes so that units can give their items to Heroes.
As have been mentioned several times earlier, the new official units, upgrades, abilities and features may cause some gameplay imbalance, as in they make certain armies more difficult to defeat. However, Blizzard has switched the focus from fights between relatively small gangs of units over to pitched battles between much larger armies; the changes to the gameplay of the official game modes are well-suited for the latter kind of engagements, because they give quicker resolutions to battles between a powerful army and another that doesn't have the necessary counters for the other.
Of course, one can only play the official game modes for so long before ennui starts to set in, even with the enhancements that Blizzard has introduced for multiplayer matches using the official gameplay mechanics.
The most important contribution of Frozen Throne is the expansion to the editor, or more likely the removal of obstacles that were once in place to prevent too much of Blizzard's game-designing technology from being handed into customers' hands.
Anyway, the greatly relaxed restrictions on designing new units, buildings, environmental objects and even map scripts now allow for very sophisticated custom-made maps with gameplay that is very, very different from that in the official game modes; they can even be different from third-party content that had been made since Reign of Chaos.
Notable examples of these include a lot of new Tower Defense games, puzzle games and even city-building simulators. However, the most enduring of the mods is the Hero-centric and wave-centric Defense of the Ancients, which then went on to create its own genre (and is still being played by die-hard fans even now, years later on).
Graphics-wise, the game does not appear to have advanced much in terms of pizzazz. There are new graphical effects, textures and models for the new powers, buildings and units, but they do not appear to be more brilliant and beautiful than the ones that are already in Reign of Chaos. The technical designs of the graphics also have not been improved by much; the game is still bound within the limitations of DirectX 8.
(On the other hand, that the game editor now allows even scripts for graphics means that mod-makers can create their own graphical effects - within the boundaries of the technical limits of the game, of course.)
The sound designs also have not been improved much since Reign of Chaos either. However, as following Blizzard's tradition, the voice-overs for the new official units and Heroes can be quite amusing.
In summary, with its slew of improvements, new features and especially the greatly unfettered game editor, Frozen Throne is a very high value expansion to Warcraft III. On the other hand, many of the new things seen in Frozen Throne could have been implemented in the original game, considering that Frozen Throne has been made using the same technology.