I also screwed up because if it only gets one counter it just gets removed the next upkeep. I put this in there incase there is other counter manipulation in the set.
12.1.8If Treefolk Assassin un-morphs choose one: If black mana was used for the un-morph cost: Destroy a creature blocked or blocking Treefolk Assassin. If green mana was used to pay the un-morph cost: Prevent all damage to Treefolk creatures this turn.
Morph 2B/G
12.1.8When CARDNAME comes into play you may pay .
When CARDNAME comes into play you may put a Mutant Counter on number of creatures. Those creatures are mutants in addition to any other creature types.
12.1.8When Unblockable Mutant comes into play you may pay U. If you do it comes into play with a Mutant Counter on it.
If Unblockable Mutant has a Mutant Counter on it it gains Unblockable.
12.1.8
Any time a creature would block or be blocked by gobbling horror, deal 3 damage to it. Creatures dealt damage this way can’t be regenerated.
If gobbling horror would deal damage to a player, prevent it. That player looses 1 life.
art: a serpent monster that looks normal infront of a warrior swinging a sword at it but it slithers around and at its head it is huge from behind.
Original idea was some form of creature that got larger, maybe by creatures dieing or coming into play. Was supposed to work well with the second ability of preventing the damage but not sure if that seems to make any sense.
Still working on that.
I also screwed up because if it only gets one counter it just gets removed the next upkeep. I put this in there incase there is other counter manipulation in the set.
Edited to add to sleepy counters when it attacks.
12.1.8If Treefolk Assassin un-morphs choose one: If black mana was used for the un-morph cost: Destroy a creature blocked or blocking Treefolk Assassin. If green mana was used to pay the un-morph cost: Prevent all damage to Treefolk creatures this turn. Morph 2B/G
12.1.8When CARDNAME comes into play you may pay
.
When CARDNAME comes into play you may put a Mutant Counter on 
number of creatures. Those creatures are mutants in addition to any other creature types.
12.1.8When Unblockable Mutant comes into play you may pay U. If you do it comes into play with a Mutant Counter on it. If Unblockable Mutant has a Mutant Counter on it it gains Unblockable.
A shame we can't have {GW2} as a symbol.
12.1.8When Mutant Beast comes into play you may pay R. If you do it comes into play with Haste.
When Mutant Beast comes into play you may pay G. If you do put a +1/+1 counter on it.
12.1.8 When Rambuncious Kin comes into play you may deal 1 damage to target creature with 1 toughness or target Treefolk creature.
12.1.8 Any time a creature would block or be blocked by gobbling horror, deal 3 damage to it. Creatures dealt damage this way can’t be regenerated. If gobbling horror would deal damage to a player, prevent it. That player looses 1 life.
art: a serpent monster that looks normal infront of a warrior swinging a sword at it but it slithers around and at its head it is huge from behind.
Original idea was some form of creature that got larger, maybe by creatures dieing or coming into play. Was supposed to work well with the second ability of preventing the damage but not sure if that seems to make any sense. Still working on that.
12.1.8 Flying When Tapping Harrier comes into play tap target creature. It does not untap during it's next controller's untap step.
12.1.8 A creature blocked or blocking equipped creature looses all abilitis until end of turn. Equip G/WG/W Equip 4
12.1.8 T: Add mana to your mana pool. T: A creature looses unblockable until end of turn. Use this ability only if you control a Forest or Plains.