There are Two Types of Creature on this Card Game

whoopsie, forgot the etbw X +1/+1 counters clause.

Yeah, just absent-minded. This challenge is now closed - Judging in progress.

There's not a lot there, a mere 41 cards, and of those only eight cards have a printing younger than eighth edition; and even their signature ability hasn't been throughly explored, let alone the rest of the thematic potential.

It's one of the more neglected tribes, as a lot of cards that could get the type attached to them just... don't. (#HumbleDefectorShouldaBeenAMerc).

Takak, God of the Forest
Legendary Enchantment Creature - Bear God
~ has indestructible as long as you control another Aura.
Bestow (If you cast this card for its bestow cost, it’s an Aura spell with enchant creature. It becomes a creature again if it’s not attached to a creature.)
Enchanted creature gets +2/+2 and has indestructible.
2/2

Time's up. I'll judge the entries now.

Poly, Gelatinous Servant 
Legendary Creature - Ooze Citizen Advisor
Poly enters the battlefield with a +1/+1 counter on her.
Other Oozes, Citizens, and Advisors you control get +1/+1 for each counter on Poly.
Whenever an Ooze, Citizen, or Advisor you control deals combat damage to a player, draw a card.
0/0

Poly here is a humanoid ooze and one of the youngest and fastest-rising public servants in New Capenna. Despite having a tentative association with the Brokers, Poly more cares about her fellow citizens than any of the five families. While she's small now, with all of the favors she's accumulated from simply trying her best to volunteer, Poly might soon become one of the biggest forces in the city... literally and figuratively. 

Cleansing Swirls 
Creature - Elemental Ooze
Whenever you sacrifice a Food, Treasure, or Blood token, you may tap Cleansing Swirls. if you do, put a +1/+1 counter on it.
“Sure, it’s a bit off to toss your overripe produce in these guys, but it’s cheaper than getting the city to take it!” — Daris
2/2

Alright, here is my entry:





And here is something that is not my entry, but I couldn't resist making it:

foureyesisafish - Poly, Gelatinous Servant: A nice design that allows for some odd tribalism. Unblockable tribal creatures and +1/+1 counter additions are a must to have in her deck. Would make a nice proliferate commander with a twist.

hydraheadhunter - Kacratore, Priestest of the Flock: Small thing first, it’s “Priestess”. The design feels… kinda clunky. It can become a board wipe for creature with 1 or less attack if you exile a creature with an activated ability that can be used multiple times. And the same actually goes for a lot of other creatures with higher power, as there are also enough pump abilities. Once on board, every creature your opponents control die as soon as they enter. I feel it’s got the ability to be too oppressive with its cheap exiling, even if it needs setup.

vizionarius - Fluvvis, Sea Enmassed: Firstly, that’s a lot of text for a full art. The design is pretty nice though. I like how the tapping isn’t permanent, and requires a player to decide what permanent they need back. Unless you proliferate their slime counters of course, then all their creatures are stuck forever. One thing I don’t like as much, is that you can also target land permanents. It does help that they don’t become tapped by the slime counters, but it will still be annoying to play against if you do target lands. I would like to see it playtested though to see just how far that goes.

ameisenmeister - Consuming Mass: Hey! The first non-legendary creature! A nice simple design, that really makes you sacrifices worth it. You do need the possibility to tap and the creatures to sacrifice in order to make this worth your while. And it’s quite a horror to have on the other side of the board.

sorsal - Cleansing Swirls: The text has a bit of a problem in my opinion, because it doesn’t explicitly state that Cleansing Swirls needs to be untapped in order for the gaining of counters to work. So you can put counters on it as much as you have tokens in one turn. Unless that’s what is meant to happen of course, but it doesn’t entirely feel like that’s supposed to happen.

pernicious - Oozing Regrets: Oof, you’re gonna have to change the wording on the countered part of the text. What we know as “fizzling” used to be a spell or ability being countered. Nowadays the spell “doesn’t resolve” instead. But the thing is, not enough players would know the interaction for sure (without looking up the rules) to allow such a cardtext to be printed. Especially not at uncommon. Perhaps if the text specified being countered by an instant or sorcery instead, it could be printed.

Idea - Body-Split Shinobi: The splitting is an interesting design, and would be strong if you can ping it yourself. I understand that the splitting is only after attacking, but as the shinobi is not blocked and it is thusly not getting damage from blockers, I don’t really get the ninjutsu ability besides if you want to ping it yourself. Which is a reason I suppose, but I feel like haste would make it less complicated, and there would be more counterplay to it.


Winner:

Sooo, 2 (exponentially) copying 4/4 deathtouch creatures for Ninjutsu? That sounds kinda busted, even if damage becomes -1/-1 counters.