The Witch, like all our character classes, was exiled from her homeland because of her crimes. Her society does not tolerate any magic use whatsoever, so her fate was sealed when she murdered those who threatened her for being different. The backstories of all the classes (including the Witch) highlight the stark unfairness that afflicts many characters in our world. She's not implicitly evil, but committed a violent crime due to her inability to control her powers. Being exiled to Wraeclast is intended to be substantially worse than a quick execution.

In terms of a specific gameplay comparison, magic users in traditional MMORPGs select a target and then cast spells on that monster in the same way that a melee character would use skills on their target. In Path of Exile, magic users can cast spells into the world and have them affect whatever they hit. The path and impact of projectiles are tracked correctly, and area of effect spells can be thrown around rapidly, chilling or burning groups of monsters that are calculated based on exact positions.

PCG: What specific abilities does the Witch possess POE currency trade , and what are one or two examples of how they change after being augmented by gems? 

Wilson: None of our characters possess any exclusive abilities, but are intended to use highly synergistic skills appropriate for their core attributes. For example, the Witch is highly encouraged to use intelligence spells such as Fireball, Ice Nova, Cold Snap and Raise Zombie. Because she's the intelligence class and these are intelligence skills, it's far easier for her to meet their attribute requirements and equip items that have intelligence sockets.

In terms of augmentation, here are some examples of support gems that have not been publicly discussed before:

"Chaining" support gem: Once the linked spell has hit one target, it replicates itself and targets another nearby valid target. For example, the fireball would explode and then launch another fireball at a nearby monster. Higher levels of the Chaining support gem cause it to Path of exile currency  target additional consecutive monsters. This support is useful for more than just the obvious damage increase, because it makes the skill somewhat fire-and-forget. The player isn't locked in place like they would be with the "Multiple Casts" support gem (which causes several copies of the spell to be cast in series).