The Cullis Gate

Awwwwww.

After reuniting with Theresa and your dog, you have one more person to meet with: Hammer! Follow the glowing trail to the Rookridge Inn to find her. After catching up, you'll have some time to kill until Theresa calls you to the Guild, so feel free to take on some quests, among other things.

Before long. Theresa will beckon you--meet her inside the Guild Cave. After some chitchat, follow them through the warp to Bower Lake. Follow the trail to regroup, then trail Garth all the way to the top of a tower. Along the way, you'll battle some more guards, as well as something called a spire shard--keep your distance and use your long-range Will attacks to take it down.

Once atop the tower, you'll have to protect Garth from the guards as he tries to open a power up the gate-if he comes under attack, it'll delay the process (but that's it--he won't die, so don't sweat it too much). Although the initial enemies that appear are weak, stronger ones will soon emerge. Stay close to Garth and unleash flourish attacks to easily take them down.

As soon as Garth opens the gate, head on through whenever your ready, as the stream of enemies won't stop until you do.