Warlock's Imp Pets

Before level 10, a warlock will only be able to summon the Imp, which is a pet that fires fireballs at enemies. It can gain access to a stamina buff called Blood Pact, as well as a damage shield called Fire Shield. The Imp is the only pet that requires no reagents to summon.

In general, the Imp represents the mage type of pet. Lots of damage output, but not a lot of hitpoints. They are best NOT taking damage alone (if you can take some for the pet he'll live longer), and they are best suited for cases when you are in a group where someone else can tank. If you use the Imp alone, you are best suited using the pet to deliver the most amount of damage as it can, while you do the same. The key with the Imp is to kill the monster before it can do too much damage to either you or the Imp.

Warlocks that have specced into Dark Pact use Imps often because of their high Spirit and Intellect. They can leave an Imp Phase Shifted and steal its mana, and the Imp will never take damage or draw aggro while it regenerates mana during the whole fight. The Imp is essentially a mana battery in these cases. The Blood Pact stamina bonus, when improved by talents, can be as effective as a Power Word: Fortitude in some cases. This also allows for quicker regeneration of mana since you have more health to fuel Life Tap.

After level 10, the Imp is generally not used for solo playing unless the warlock has run out of soul shards, since his utility for leveling is outstripped by the voidwalker and succubus. Though, some warlocks choose to "AoE" grind mobs like some mages do by casting all DoTs on one target, choose new target, DoT that one, and so on. For this the imp is useful as both a mana battery and for the stamina buff.

In end-game raids the Imp is useful primarily for Blood Pact. The fact that phase shift prevents him from dying as long as he doesn't use firebolt is also a plus. The Blood Pact ability is regarded so high that there are guilds that require warlocks to always use the Imp. However, many players that request the presence of an Imp don't have a full understanding of Blood Pact (which is limited to a 20 yard range). As warlocks are a ranged class, they will usually try to stay at a maximum range, which will be around 30 yards. That means that the melee class in the party may not get the benefits of the Blood Pact. In boss fights, a good warlock will step forward and request the Imp to stay at a position where most players are inside the 20 yard range, and then step back again to a safer distance.