Diablo II/Fallen Angel

The first quest in Act IV can be activated by talking to Tyrael:

If you talk to Tyrael or Deckard Cain before leaving, or return after activating this quest by finding Izual in the Plains of Despair:

This quest is optional, but it's well worth completing. The Plains of Despair are just beyond the Outer Steppes, which are at the bottom of the stairs leading down from the Pandemonium Fortress beyond the gateway in its southeast wall.

Outer Steppes
The Outer Steppes are randomly populated by three of the following six monster types: leaping s, corpse-spitting s, mana-draining s, s, s (which spawn s) and fire-breathing s. There are also s.

The Pandemonium Fortress is on its northwest side and the entrance to the Plains of Despair is on the perimeter of one of the three other sides: since the stairs down from the Fortress take you to the west corner of the Steppes, it's best to travel right upon entry (even if the entrance is on the northeast side, it's likely to be close to the east corner).

Plains of Despair
The Plains of Despair are similarly populated to the, except lightning-casting s replace Cliff Lurkers. The entrance to the is on the perimeter of one of the three other sides: if you find it before Izual, you may want to enter, search for and activate its waypoint before returning to the Plains (it's next to the stairs down to the ).

Izual
../Animal/

Save yourself!

This quest is activated when you approach Izual if talking to Tyrael has not already done so:

If you return (again) before destroying the 'demon':

Izual is a melee attacker who can cast. He isn't particularly dangerous and he never has any Unique bonuses, but it can take a while to destroy his host without or  to reduce its life by a percentage rather than an absolute amount. Once you've done so, Izual's spirit is released and any other monster in the vicinity is killed (although no experience is received for these).

You don't need to do this, but you might as well:

If you talk to Deckard Cain:

See Tyrael for your reward: two skill points!