Zombies make the game enjoyable in short bursts, but aren't enough to bring it above overall mediocrity.
The three are given a chance to exact their revenge on the king after being brought back to life by an individual known as 'The Beast' and becoming 'Undead Knights' with the power to turn the living in to the undead. This is an interesting premise, yes and Undead Knights definitely features some interesting ideas and creativity, but the game on a whole is a bit of a loud, bloody mess without one specific redeeming feature.
To get it out of the way, the single worst thing about Undead Knights is the nightmarish soundtrack. To get an idea of how bad the music is here, imagine a chainsaw being put through a washing machine on spin cycle with a sprinkling of grenades and two note heavy metal riffs. Let's just say, this game on full volume is… an experience.
Before I go to town on ripping this game to pieces, as mentioned before it does feature some interesting concepts. You turn your hapless enemies into your undead allies by pressing the circle button and waiting for a red circular gauge to fill up before they succumb. This adds a small element of strategy early on as you can be vulnerable to attack during this time. This would be ok if it lasted, but after purchasing upgrades from a menu available between levels, you will be able to deliver damage and transformation fast enough to throw any strategy out of the window.
Some other upgrades available to you include the expected health increases and basic combo's (which are very basic) but at least give you something to work towards and create a slight feeling of character progression, and being an upgraded powerhouse with an army of undead can be pretty fun in short bursts.
When you do manage to amass a group of undead, you can order them to attack other enemies, fences and other defensive fortifications as well as do certain contextual actions such as form a bridge or gather around you in a defensive manoeuvre. This system controls relatively well but the crosshair you use to direct the undead does feel slightly clunky and inaccurate which is a shame given that controlling the undead is the game's main selling point.
At its best the game feels like a horror themed combination of Dynasty Warriors meets Overlord, which is actually surprisingly refreshing, however the games' neat ideas and even its main gimmick aren't expanded upon anywhere near as much as you might like.
Despite the zombies being the best part about the game, they also seem to come with a number of questionable design choices. For example; regardless of how well armoured or powerful the enemy you just turned into a zombie, it will be exactly the same as all the other weak, blue bodied corpses that you have shambling by your side. Different zombie types would have gone a long way to adding some much needed variety. Whilst this distinct lack of variety hurts the game during anything longer than short play sessions there are a few interesting uses of the zombies in combat, such as the ability to throw them to stun enemies, or latch onto bigger foes, while you watch on in glee as it is pulled to the ground with blood spurting from its body.
It would have been great to spend upgrade points on your zombies, allowing the building of an unstoppable undead army with enhanced abilities, but unfortunately no such features are present.
One unfortunate side effect of zombies in a standard hack n slash formula way the game seems to be deliberately obtuse at times just to force you to use zombies and keep them relevant. For example, while you can merrily smash your way through barrels, crates and pots in order to find souls and health items, you can't smash down fences or gates or even kill enemies with a shield without help from your undead. While it is disturbingly satisfying to have a horde of zombies eat a well armoured knight alive while he screams for help, the fact that you can't land a good hit on him with your huge melee weapon detracts from the feeling of power you have as a super powered undead knight in your own right.
Ultimately this game has a huge number of flaws. Undead Knights can be very repetitive, the music is awful, there are a bevy of graphical oddities and a number of questionable design choices, but look past all these and you may have some simple gory hack 'n' slash fun. There are also a couple of simplistic multiplayer mini games, playable over adhoc mode, but they serve as nothing more than a slightly amusing distraction.