9 Lithomantic Barrage Players familiar with Rending Volley from Dragons of Tarkir should already be aware of the value this card offers
Note that it enters with two +1/+1 counters for eachg creature sacrificed, not just for each time you payed X, so if each of your opponents - but not you - sacrifices a creature, Gluttonous Hellkite enters as a 9/9 if you paid 4 mana for it
While the obvious choice would be to use a legendary werewolf card, there are only two dedicated legendary werewolf creatures for you to pick from
Cards like Whisperwood Elemental and Mastery of the Unseen were Standard mainstays the entire time they were legal in the format
Ashiok, Wicked Manipulator provides card draw and poops out loads of tokens that can grow really large over the course of a longer game
Dimir is often seen as a Storm combo deck in Eternal formats, putting together cards like Ad Nauseam, Dark Ritual, Cabal Ritual, and storm win conditions like Brain Freeze and Tendrils of Agony