Malice is what makes monsters decide who to attack: the player with the highest amount of Malice will always be targeted. It cannot be tracked or seen in the usual game interface.
Causing damage (skills or attacks) to a monster will generate Malice towards the attacker.
Healing players or applying buffs will also generate Malice on every monster in combat with the targeted character.
One can think of it as hate: the more you hurt a monster, or help who's hurting him, the more it hates you.
Importance of Malice in Groups
In practice, a group will always want the monsters to attack a tank . This archetype has the only tools to generate extra Malice, and they should be employed to keep enemies from more fragile allies.
Protecting the healer is a vital part of running dungeons, as any damage can disrupt his or her healing spells and quickly lead to dead players.