Does a creature enchanted by multiple Auras die if one of the Auras has an illegal target?

When a player casts a spell or an effect causes an Aura to become attached, the Aura's target must be legal. However, once an Aura is already attached and sitting on the battlefield, legality is checked at a different moment: state-based actions (CR 704.5n) ask whether an Aura is attached to an object or player it could legally enchant. If the answer is no, the Aura is put into its owner's graveyard as a state-based action.

Crucially, this only affects that specific Aura. The creature it was attached to remains on the battlefield unless some other rule or effect removes it. Any other Auras that are still legally attached to the creature continue to function normally (CR 704.5n, 303.4c).

A target can become illegal in several ways: the creature gains protection from the Aura's color or type, the Aura's own text changes such that the creature no longer fits its enchant condition, or the creature's characteristics change. The game checks state-based actions continuously, so the illegal Aura is removed the next time state-based actions are checked.

Concrete example: You control a creature enchanted by both Pacifism (enchant creature) and Lifelink (enchant creature). Your opponent casts a spell giving your creature protection from white. Pacifism is white, so it is now illegally attached; state-based actions put Pacifism into your graveyard. Lifelink (also white) is similarly illegal and is also put into the graveyard. The creature itself, however, is perfectly fine and stays on the battlefield.

If only one of two Auras becomes illegal — say one is white and one is blue, and the creature gains protection from white only — then only the white Aura is placed in the graveyard; the blue Aura and the creature remain unaffected.