Warlock's Doomguard Pets

At level 60, you obtain the Curse of Doom spell, and can quest for the Ritual of Doom. Curse of Doom, when dealing the killing damage to any mob, has an estimated 10% chance of summoning a Doomguard. Ritual of Doom will always summon one, at the cost of the life of a party member. A Doomguard must be enslaved in order to command him. The Doomguard is more frail than the Infernal, but has far more abilities. He attacks in melee, and has a devastating crippling attack (a spell called "Cripple") which slows opponent's attacks and movement, and he can stun with War Stomp. He can cast Rain of Fire, although this consumes most of his mana. The tactics for using Doomguard are similar to the Voidwalker, except that Doomguard does tremendous amounts of damage and may require some healing. Generally, you turn off the autocast for Rain of Fire, but let him warstomp and cripple at will. In PvP, Doomguard will wreak havoc on the enemy with his stuns and cripples, unless one of those enemies is another warlock, in which case he can be banished immediately.

As always, cast a Curse of Shadow before enslaving. When your five minutes are almost up on the Doomguard, have him use up his mana by casting a Rain of Fire and get ready for a fight when he breaks enslavement.

Ideally when you suspect you will not be able to enslave again (demons become more resistant to it the more you recast it on them) try to get it killed. Even if you forget that it is about to break out, and it has all of its mana and health, defeating a Doomguard solo is not too hard. Banish it first since it will probably get on you if you've forgotten about the time anyway. Then back up (and bandage if needed), and fear it. Oddly enough, this huge hulking mass of evilness is scared of you.