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The entire perimeter of the temple is patrolled by Yuan-ti, so you'll find yourself first making use of Zhai's sneak attacks to dispatch of as many as you can. Be patient and keep her in the shadows until you find the perfect opportunity to silence each Yuan-ti. If you're spotted, try and kill the Yuan-ti that saw you before it has a chance to ring the gong and bring on more of the snake-like creatures. The final two Yuan-ti in front of the entrance door can be quite tricky since there is quite a bit of space between Zhai and the nearest darkness, so be very careful and use a full frontal assault if necessary. Once these two are taken out, don't go in the door just yet - there is a chest and a bag atop the ledge just off to your left.

Once inside the temple, a cutscene will commence that shows a Yuan-ti Sorcerer using the Demon Stone for some sort of ritual. Before you can stop him, though, you're descended upon by a whole army of Yuan-ti and are forced to fend them off first. Destroy the rope bridges to keep some of the creatures from crossing, then finish the rest of them by either hacking them to death, pushing them over the side, or shoving them into the fiery pit. After you've dispatched what seems like a countless number of Yuan-ti, the Sorcerer will finish his ritual and conjure a huge demon. The demon must feed on living sacrifices to grow in strength, so you must destroy the Shamblers that are marching toward the demon to keep it from feasting upon them.

Since the Shamblers are under mind control, they don't even fight back. Just when you think it's going to be too easy, though, the Yuan-ti begin another wave of attacks and you must juggle between keeping the Shamblers from feeding the demon and defending yourself against more of the serpentine enemies. If you keep the beasts from crossing over to the demon long enough, its hunger will grow and it will eventually eat the Yuan-ti Sorcerer that originally summoned it. After this happens, you'll be able to reach the platform to the Demon Stone itself. Since the Demon Stone is surrounded with a shield, though, you'll have to attack it with everything you have before you can reach it.

Cycle through the three characters and use their melee attacks to bring the shield surrounding the stone down as quickly as possible. The demon will not allow you to inflict too much damage on the stone's shield before it starts crushing you with its fist, so you need to rush in and take a few swings and then rush back out of the demon's range. Keep this procedure up until the stone is free, after which another cutscene will show the demon fall to its death in the water far below. Now that the Demon Stone is in your possession, it will actually regenerate health for Illius every time he fires a spell. Not bad, eh?