My first thought when reading this was that these are
strictly better than pillars in almost all cases. This means they would be necessary to grind for even basic PvP, and even for AI3+ grinding if the AI were using them prevalently. That's quite a barrier to add to the game in my opinion.
My next thought was, what kind of ability can be given to something that is, at its basic form, free and generates quanta? It takes a lot to achieve what a Death Monolith does - a vulnerable 2
creature must stay alive one turn, then you must spend one
to add the poison. The only advantage is that it's reusable, but you're probably going to be running multiple Death Monoliths.
My third thought was to have them be situational, so that they won't be a 'must-have' card. However, this would probably result in a few of them being extremely popular while others become next to useless.
So I finally came to this conclusion: they could have a passive ability, called Legendary - you can only have one of it on your side of the field at any time. If you play another, it dies at EoT (the CiP effect would still work, I suppose). They could alternatively have their own slot, much like the Weapon/Shield slots. This would let them be reasonably powerful, while not being necessary. I also thought it might be better to have them be stronger late game, as drawing a pillar later is often useless.
I like the overall idea, it's a good way to show the specialty of each element. Now that I've spewed my thoughts, here are some ideas. The values within can be modified, they are just basic ideas.
: You become immaterial for two turns.
: Deal 1 damage to target, plus 1 if it is not airborne.
: Target creature gains
Dive for one turn.
: Gain 1 life, plus 1 for each creature on your field in the top and bottom rows.
: Gain 1 life, plus one for each creature that died last turn.
: Target creature gains +0|+2 for two turns.
: Target permanent becomes immaterial for two turns.
: Move 2 random quanta of the opponent to other types of quanta.
: Target creature becomes a random, different creature for one turn.
: Target creature gains +2|0 for one turn.
: Target creature gains Momentum for one turn.
: Target creature gains +2|-1 for two turns.
: Target creature gains +1|+1 for two turns.
: Target creature with ATK less than 5 attacks twice this turn.
: Gain 1 life, plus 1 for every 2 bioluminescent creatures you control.
: Heal target creature for 5 HP.
: Target creature is resummoned.
: Return 1 pillar from target stack to its controller's hand.
: Destroy one empty middle row creature slot for 3 turns.
: Gain 1 quantum of the target pillar's element.