When Mairsil, the Pretender enters the battlefield, you may exile an artifact or creature card from your hand or graveyard and put a cage counter on it. Mairsil, the Pretender has all activated abilities of all cards you own in exile with cage counters on them. You may activate each of those abilities only once each turn.

{4}, {T}: Roll a d20. Each opponent exiles cards from the top of their library until they exile an instant or sorcery card, then shuffles the rest into their library. You may cast up to X instant and/or sorcery spells from among cards exiled this way without paying their mana costs. 1—9 | X is one. 10—19 | X is two. 20 | X is three.

Whenever a creature enters the battlefield, destroy it. {0}: Destroy Lethal Vapors. You skip your next turn. Any player may activate this ability.

This spell can't be countered. +2: Each opponent gets an emblem with "At the beginning of your upkeep, this emblem deals 1 damage to you." −3: Chandra, Awakened Inferno deals 3 damage to each non-Elemental creature. −X: Chandra, Awakened Inferno deals X damage to target creature or planeswalker. If a permanent dealt damage this way would die this turn, exile it instead.