Deal 1 damage to a minion. If that kills it, draw a card.
If your spells look like horrifying skulls, let's be honest, you should get to draw some cards.
 How to get
Mortal Coil x 2 are a reward for raising a warlock to level 4.
In addition to the obvious removal potential, it is important to note that this spell can be cast at your own minion in order to draw a card (particularly useful in decks that are designed to draw as many cards as possible). It can also be played as a last ditch effort to draw a card that could save you from losing (such as a taunt) when at low life.
It is very helpful to increase spell damage for Mortal Coil in particular, as it will allow it to take out medium sized minions such as Shattered Sun Cleric and draw a card for a mere 1 mana.
Mortal Coil is a talented warlock spell from World of Warcraft. It causes the target to run in horror for 3 seconds, and restores a portion of the warlock's health. It is very useful as a form of crowd control, as well as a regular method of maintaining health levels.