I feel like some of them might be incredibly overpowered but lets hear your thoughts first.
Yeah, perhaps a touch.
First: some say "one turn", others say "1 turn". You might want to standardize it.
Blood is ok, in my opinion.
Frogs+Mayhem=ouch. It's also a great combo combined with Priests of Christ.
I'm all right with Gnats. A turn limit would be more manageable, but it might tone it down too much.
2x Flies in T2 means instadeath. At the very least, add "limit oneper territory".
I love pestilence. Any card that tosses opponent's cards is cool in my book.
Boils is practically SoG. Play it before block and walk in.
Hail may be a bit on the strong side. An "or" may help. Otherwise, great.
I like locusts.
Darkness is good.
I like the instead on death. Good balance. It may be construed, however, that one dominant could save all three evil characters. Might want to clean up the wording a bit.
Moses will never again lose a FBTN battle.
Remember that Micah can recur blood, frogs, gnats, and flies.