Evoker
An Evoker is a form of Specialist Wizard in Dungeons & Dragons. Whilst Evocation is used in some settings in much the same way as Conjuration, meaning to draw upon the power of otherworldly beings, in D&D, it means something else. Evocation in D&D is the School Of Blowing Shit Up, using elemental damage to fry, freeze, electrocute, shock, dissolve, crush, rend, mangle, maim and eviscerate whatever happens to be standing in your way. The trusty Fireball and Lightning Bolt spells are iconic Evocation spells.
Ironically, around the time of 3rd edition, Evokers began to be looked down upon as being "too weeaboo", with far greater love being directed at the "utility wizard" who focused on assorted spells that weren't combat focused, but let them do anything. Partially this was due to to the new mechanics for that edition; "Save or Suck" spells, which tended to cripple or outright destroy a foe immediately if they failed their save, were simply considered more resource efficient than painstakingly whittling down enemy hitpoints.
4e Evoker
The Evoker returned as a subclass for the Mage in Dungeons & Dragons 4th Edition. Being an Evoker was handled as a set of three features gained by choosing that specific magical school, and which were acquired at levels 1, 5 and 10. A Mage could also dabble in Evocation by taking the 1st and 5th level Evocation school benefits at levels 4 and 8.
- Evocation Apprentice: When you roll damage for an arcane evocation power, if any of the dice come up with a result of 1, pick one of them, reroll it, and use the new result.
- Evocation Expert: You gain a +2 bonus to Endurance checks and Intimidate checks.
- Evocation Master: When you use an arcane evocation power that deals one or more specific types of damage, you ignore a target’s resistance to any of those types of damage. You do not ignore any immunities the target might have.
5th Edition's Arcane Tradition
Evokers are... well, really, what's to say? They blow shit up better than any other wizard. They start off with Sculpt Spells at level 2, letting them make safe pockets in their evocation spells to avoid blowing up their allies or non-coms who get in the way. Or, well, at least ensure they only get singed instead of fried. At level 6, Potent Cantrip means that even Evocation cantrips get to do half damage against critters that make their saving throws against them. The humble Empowered Evocation, a 10th level feature, lets an Evoker add their Intelligence modifier to the damage rolls of any Evocation wizard spells they cast. Finally, at level 14, they gain the Overchannel ability. What's that do? Once per long rest, they can cast an evocation spell of level 5 or lower and automatically do max damage. Once they've done so, if theydo it again without resting, they take 2D12 necrotic damage PER level of the spell they're casting like this. And if they're dumb enough to keep casting overchanneled spells? They keep taking necrotic damage, only the damage goes up by another 1D12 per time (so their third overchannelled spell is 3D12 damage per level of the spell, their fourth is 4D12, etc). RAW, you could originally overchannel your cantrips all day long with no ill effect (2d12 * 0 = 0), but this was later errataed so that you couldn't overchannel cantrips any more.