Dragons of Silumgar's brood begin to digest their prey even before consuming it, letting their caustic breath do much of the work.

Noxious Dragon

Flying
When Noxious Dragon dies, you may destroy target creature with mana value 3 or less.

Commander Legends

Flying
When Noxious Dragon dies, you may destroy target creature with converted mana cost 3 or less.

The List

Battlebond

Iconic Masters

Fate Reforged

A face-down creature has a mana value of 0. However, its mana value changes when it's turned face up. Thus, if a creature is turned face up in response to being targeted by Noxious Dragon's ability, it may become an illegal target.

If a creature on the battlefield has {X} in its mana cost, X is considered to be 0.