MTG Salvation

Corrupting Visions 6U
Sorcery (C)
Supplicate (Each creature you put a -1/-1 counter on while casting this spell pays for 1 or one mana of that creature’s color.)
Draw three cards.

Blightsteel Knight 3B
Creature - Zombie Knight (U)
Corrupt (Whenever this deals damage to a creature, 1 of that damage is dealt in the form of a -1/-1 counter.)
Creatures you control with a -1/-1 counter have corrupt.
3/3

Horror of the Tangle 5G
Creature - Beast Horror (C)
Corrupt (Whenever this deals damage to a creature, 1 of that damage is dealt in the form of a -1/-1 counter.)
Whenever Horror of the Tangle blocks or is blocked by a creature with a -1/-1 counter, it gains trample until end of turn.
6/5

Cleanse with Blightfire 3R
Instant (C)
Weaken 2, then Cleanse with Blightfire deals 2 damage to each opponent that controls a creature with a -1/-1 counter on it. (To weaken 2, choose a creature with the greatest toughness among creatures you don’t control. Put two -1/-1 counters on that creature.)

Gitaxian Recall U
Sorcery (C)
Return target creature to its owner’s hand. If that creature had a -1/-1 counter on it, proliferate. (You choose any number of permanents and/or players with counters on them, then give each another counter of a kind already there.)

Numberless Nim 1B
Creature - Zombie Horror (C)
Corrupt (Whenever this deals damage to a creature, 1 of that damage is dealt in the form of a -1/-1 counter.)
A deck can have any number of creatures named Numberless Nim.
2/1

Quote from TywinLannister »

I'll note some templating issues for you:

Supplicate (Each creature you put a -1/-1 counter on while casting this spell pays for 1 or one mana of that creature’s color.)
It isn't clear here that only your creatures can help*, I know a comp rules entry could help here, but convoke starts with "your creatures can't help cast this spell", you could try:

Supplicate (You may corrupt your creatures to help cast this spell. Each creature you put a -1/-1 counter on while casting this spell pays for 1 or one mana of that creature’s color.)

*Unless you want to use their creatures as well?

I doubt that necessary. Convoke didn't have "Your creatures can help cast this spell" originally. It was only added in the core set when it was found to decrease comprehension complexity even though it was adding words.
However the action of Supplicate is far less easily intuitive. Your not tapping it like a land which is immediately understandable as relating to the cost. Instead your adding counters which isn't usually assosiated with mana payments. I'm not saying I don't like the wording suggested just that I'm not convinced it is as necessary or useful as the convoke additional wording.

Supplicate - Might be dangerous depending on the other cards in the format since you can use the same creature multiple times in the same turn. And in larger formats with creatures that use -1/-1 counters like Morselhoarder or creatures that can gain a lot of +1/+1 counters to compensate the cost might not even matter.

Corrupt - Is this supposed to stack in multiples like with Cavalry Master? As a triggered ability it would, but in order to replace damage with a different event it needs to be a static effect. Then it could be treated like lifelink where multiple instances are redundant. Something like:
Corrupt (Each time this deals damage to a creature, the first of that damage is dealt in the form of a -1/-1 counter.)

Horror of the Tangle - This only needs to be "Whenever CARDNAME becomes blocked ..." Unless you have some large mechanical them where having trample while blocking is important.

Weaken - Reverse bolster with -1/-1 counters should probably be limited to "creatures your opponents control". Otherwise it is very bad in team environments because you will end up having to weaken your teammate's creatures.

Quote from silvercut »

Supplicate - Might be dangerous depending on the other cards in the format since you can use the same creature multiple times in the same turn. And in larger formats with creatures that use -1/-1 counters like Morselhoarder or creatures that can gain a lot of +1/+1 counters to compensate the cost might not even matter.

Because of the "each creature" clause this doesn't mean you can use the same creature multiple times.. At least the intention was that you can only put a single -1/-1 on each creature you use to reduce cost.

The Horror of the Tangle text is simply because it is a cycle, I agree trample doesn't do anything defensively.

The rest are good points and I'll see what I can do to adjust wording.

Doombringer: What silvercut meant (I believe) was that you can keep supplicating one creature with multiple supplicate spells.

Quote from TurboJustice »

Doombringer: What silvercut meant (I believe) was that you can keep supplicating one creature with multiple supplicate spells.

Oh sure. Your not really going to have a board state left though...
Like delve or convoke I definitely have to treat the mechanic very carefully.

Supplicate - Exactly. I didn't make that clear enough. My concern would only be if there are any supplicate cards that lend themselves towards combos, then mid- to high-toughness creatures (like early walls that you play to stall your opponent) can fuel multiple supplicate spells.

Horror of the Tangle - If it is part of a cycle and needs that trigger, I would look for another ability. If you see only this card, then it could be potentially confusing.

Quote from Doombringer »

Convoke didn't have "Your creatures can help cast this spell" originally.

Tapping your own creatures for various beneficial effects is common to Magic. Putting negative counters on them is not. Supplicate's reminder text leads me to think I can put the counters on creatures I don't control and makes me want to put as many of the counters as I can onto my opponents' creatures.

Yeah, it's really not clear that Supplicate only puts -1/-1 counters on your own creatures. "Each creature you control which you put a -1/-1 counter on" would make it clear and cost nearly nothing in complexity, right?