Mesmer bis fun -
https://www.guildwars2.com/en/the-game/professions/mesmer/
But basically, they summon illusions of themselves with surprisingly lifelike AI. Then they can explode their illusions to deal a ton of damage, slow their enemies, confuse their enemies, or become shortly immune to damage. It's incredibly confusing in a battle, let alone a group battle. The way in which you summon your illusions differs by weapon; some of them can be extremely confusing to tell apart from the actual character, making the mesmer unbelievably fun in pvp. Also, we have a blink that shoots you where you click
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