Only Soul Eater I know of is The Duchess (giant Merveil's Daughter). I just killed her on my DW/EV char. Required lots of kiting and killing adds to refill mana pots. Adds count as kills, but not souls, so you can refill pots, but not Vaal Gems (bummer). Of course, killing adds also provides more souls [for The Duchess to consume]. So, yeah.