Why not just have a single 'summon' ability where a random Primal appears (you have no control over who) that does auto-attacks & with the ability for a signature attack, like Enkindle? They would last for a set length of time before vanishing & being ready to be resummoned, a bit like how AST cards work. Additional features could be added that allow the player to 'influence' who is likely to be summoned but it would still be random. Most importantly, the stats of the Primal & their attacks would be identical across all summons so there'd be no "better" Primal.