Merger: I doubt you can target two creatures at once with the current programming. I made a similar card before too... oh fine, if I made it, it has to be good. A bit too pricy for just added vulnerablity to Gravshield, Freeze and whatever not to mention the both-side lolbotomy.
Sprunk: Bit too pricy for this highly brittle bonewall whittler, again.
Bonfire: Getting multiples of those at once would be deadly. I'd splash Fire into Aether and exploit those and Quints, they could even be better than the Lavagolems by then.
Stasis: So, I pay 5-6 Time and a turn wait for just one turn of embargo? Weak.
Hasten: Precognition is way better.
Flesh crawler: Costly. Fairly weak, becomes brittle after nibbling a few times, and so on.
Phantom: I can see how this is a bacon-saver when you're at 0 cards, but... still pricy.
Sacrificial Altaïr: If this isn't usable more than once per turn, it's rediculousely weak. If it is, then... fine, I guess. Not that I know any uses of mass Death quanta.
Lob: It's fine. Weak spells should cost way less than their ability counterparts as every piece of deckspace is valuable and the weak ones may be just too weak to be useful to take.
Baptist:
This card has one big problem that I see over and over again on this forum. If you use this card in your deck you have to have skeletons.
It a problem in deckbuilding because it limits your options dramatically. You don't have Skeleton Captain with Frogs, you don't have Skeleton Captain with Photons, you always have Skeleton Captain with Skeletons.
If you look at the current cards in Elements, there are no cards that require you to have another specific card to be effective (at least none that I can think of), and that's what I like about Elements.
And if there are no Skeletons, then what can I do with this card? Get it in rear?
Knight and Paladin: Costly, costly, costly... for 5 Light I can have a freely targetable abiliy version of Blessing, not this one-target thing. It's like growth this way, deserving to cost 2 at most.
Piety: And upgrade does Luciferin too. No, not srsly. This would be like impossible to code, as it'd require the very cards to change... you'd have to have Light Phase Spiders, Light Shriekers, Light everything costing Light to play.
Sacrifice: See Aflatoxin. Immediate removal of a card is unprecedented, so I suggest it poisons the target for 2 and the damage taken heals the card's owner... no, wait. That'd be ridiculously weak. Unacceptable as it is now, anyway.
Sacrifice: Too much OP with flying titans.
Why mess with 2-3 elements 3 cards when you can just Miracle?
Ball Lighting: Upgraded Spork is called that. Also... well, if the enemy doesn't have Aether, he ends up with a 3/1 you practically funded.
Contract of Souls: It sounds alright, and particularly cruel when conjuncted with Earth/Darkness Denail.
Unfaithful: Awesome attacker, wanna buy. Imma just use one Bond and it'll be awesomer still.