Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token that's a copy of this creature that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

Whenever Broodbirth Viper deals combat damage to a player, you may draw a card.

Whenever Marsh Viper deals damage to a player, that player gets two poison counters. (A player with ten or more poison counters loses the game.)

Whenever Ohran Viper deals combat damage to a creature, destroy that creature at end of combat.

Whenever Ohran Viper deals combat damage to a player, you may draw a card.

Other tapped creatures you control have deathtouch.

Other untapped creatures you control have hexproof.

, : Untap another target creature or land you control.

, , Sacrifice Soulcoil Viper: Return target creature card from your graveyard to the battlefield with a finality counter on it. Activate only as a sorcery. (If a creature with a finality counter on it would die, exile it instead.)

Enchant creature

Enchanted creature gets -1/-1, and its activated abilities can't be activated.

Deathtouch

Bloodrush — , Discard Wasteland Viper: Target attacking creature gets +1/+2 and gains deathtouch until end of turn.