Diablo/Diablo, Lord of Terror

Cain fears for the worst, for him, there is a possibility that maybe Albretch is Diablo's vessel. He will tell you to end this terror.

There isn't much to do, backtrack to level 15 and go down through the pentagram. You'll find yourself at level 16, Diablo's Lair. This lair is pretty messed up and filled with blood knights and advocates.

It's a complex system of levers. There are four of them. They are all on the end of large areas, pretty similar to a maze. Go pushing them until Diablo comes out. Have resists against magic and fire and a good armour. Those demons, including Diablo himself, can kill you fast if you don't stay alert.

Diablo is pretty weak against almost all the spells but Stone Curse – he will not get paralysed. However, a melee fight will be pretty tough since he is surrounded by minions. Keep drinking potions if you get close to death. Cast spells until he dies if you are a sorcerer, or attack from a safe distance if you are a rogue. However, if you are a warrior, try to use a vicious axe, as that may help a lot.

Diablo can cast Apocalypse, so beware.

After killing him, enjoy the ending cutscene.