He then corrected himself later on saying it was random, also the forum says it is random

Tar Creeper, Primordial Drake and Wyrmguard all get buffs and it’s not that understatted, personally I don’t think you need that many as the effect is that good. You are still getting a 6 mana 55 which isn’t incredible but still. May add some more but we’ll see

Oh yeah forgot about that, maybe we’ll see a new higher cost spell will be unveiled but we’ll see !