A few more custom designs -- I'll probably just use this one thread for custom cards.
For a lot of these, they're based on mechanics I'm using for a custom set. I'm borrowing arcane/splice from the Kamigawa block, and trying to work out a few new ways to use them, since it was an extremely narrowly-played mechanic and "Arcane" was oft treated just as a creature type, if you catch my drift. There's also just generally a mechanic based on high CMC -- a lot of cards of high CMC are basically just lower-cost cards but with cost reduction effects. Hopefully this still works as I'm intending it to. (The threshold is 7+, and I have no idea how I came to this conclusion right now -- there was a good reason for this at some point, though.)
Synchronous Madness | B
Sorcery | Rare
Each player reveals his or her hand, then discards all cards he or she revealed that share a name with another nonland card another player revealed.
Evolutionary Procession | 1G
Sorcery - Arcane | Uncommon
Search your library for a creature card or land card, then reveal it. Shuffle your library and put that card on top of it.
Draw a card for each card spliced onto Evolutionary Procession.
Bonded Lightning | 2R
Instant - Arcane | Uncommon
Bonded Lightning deals 4 damage to target creature or player. If Bonded Lightning is spliced onto another spell, instead it deals 6 damage to target creature or player.
Splice onto arcane 4RR
Ghastly Servant | 5WW
Creature - Spirit | Uncommon
Ghastly Servant costs 4 less if you have at least two other cards in your hand.