Quick aside a number of players are mad that poisonous specifies "combat damage" since so many poison decks make use of Psionic Gift-type interactions to deliver the poison
These include creatures such as Agent Frank Horrigan (indestructible, proliferate), Alpha Deathclaw (destroys permanents), Consuming Aberration (mill), Ezuri (proliferate, card draw), Fathom Mage (evolve, card draw), Lily Bowen (+1/+1 counters, life gain), Marcus (card draw, +1/+1 counters), and many more
As such, have fun playing Pauper and enjoy some tips on beating up on Red decks
Instead, it has a cast or attacks trigger
X: Legends Awakened (Ultra Rare) $102.15 Making A Massive Impact Mewtwo LV
If your opponent activates a card or effect, while this card is a Continuous Spell (except during the Damage Step): You can Special Summon this card [with another effect on top]