June 10, 2022 · Commander Legends: Battle for Baldur’s Gate
As a bestowed Aura spell begins resolving, if its target is illegal, it ceases to be bestowed and the effect making it an Aura spell ends. It continues resolving as a creature spell. See rule 608.3b.
September 24, 2021 · Innistrad: Midnight Hunt
As a bestowed Aura spell begins resolving, if its target is illegal, it ceases to be bestowed and the effect making it an Aura spell ends. It continues resolving as a creature spell. This is an exception to rule 608.3a.
April 22, 2021 · Strixhaven
If a bestowed Aura becomes unattached, it ceases to be bestowed. If a bestowed Aura is attached to an illegal object or player, it becomes unattached and ceases to be bestowed. This is an exception to rule 704.5m.