GrimTools: https://www.grimtools.com/calc/bVAjme7Z
Call the camera crew, I’ve got the green screen ready!
This build smothers the screen with green acid lightning and auras, covering all nearby enemies in widespread dot damage. This is a high elemental-to-acid conversion caster build, with green Wind Devils (and their green lightning)!
This build is not an overly powerful build at all - it is neither top tier damage or survivability, so enjoy it for what it is - a fun concept build. I’m sure it can be improved on a lot, but it’s not a bad starting point for the idea. 
With strong ele to acid conversion, I’d specifically chosen devotions that provide good elemental dots, which translate to stacking poison dots. This build has 100% lightning and fire to acid, 50% vitality to acid and 50% cold to acid damages. As a result, it has a lot of elemental AND poison damage spell effects, making it appear to be very ‘eldritch’ in nature. 
It also summons eldritch talons and webweavers to give it that legit eldritch look 
With all buffs and totems, wind devils etc up, this build can achieve ~1.2m damage per second on the combat dummies in Conclave, with dot damage reaching about 270k per second. For single target DPS, it’s clearly nothing special, but I suppose it deals about this much damage equally to everything in the area due to almost every attack being some kind of AOE/multi-target attack, so it ends up clearing through groups of enemies as fast as it clears through individual enemies.
Enjoy!