Mire Boa

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
{G}: Regenerate this creature. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Seshiro the Anointed

Other Snake creatures you control get +2/+2.
Whenever a Snake you control deals combat damage to a player, you may draw a card.

Snake Pit

Whenever an opponent casts a blue or black spell, you may create a 1/1 green Snake creature token.

Forest

Noose Constrictor

Reach
Discard a card: This creature gets +1/+1 until end of turn.

Snake Basket

{X}, Sacrifice this artifact: Create X 1/1 green Snake creature tokens. Activate only as a sorcery.