Illusion Magic is an attribute linked to skills. The skills in Illusion magic are a mixed bunch. There are skills like Arcane Echo, which copies the next spell you cast for a brief time, that allow the Mesmer to circumvent the game’s normal rules – in this case that you can only have one of each skill on your skill bar at a time. And there are skills like Conjure Phantasm, which causes your target to suffer health degeneration, that let the Mesmer, cause some damage. Its skills work mostly indirectly, slowing an opponent or causing them to lose health over time or otherwise weakening them or strengthening the caster. Overall, if Domination is the anti-caster line, then Illusion is the anti-melee line as it includes both ways of slowing foes to prevent them from closing to melee range as well as ways of avoiding damage once they actually do.