Rebuttal
Card Text & Abilities
[Reaction] (Play any time, even before spells and abilities resolve.) Choose a spell with Energy cost no more than [4]. You may pay [A]. If you do, gain control of it and you may make new choices for it. Otherwise, counter it.
Official Rules FAQ & Clarifications
3 Official FAQsIf you are remaking choices in this way, any choices you choose not to remake must be legal choices. You can’t choose to have some but not all choices be legal choices. Of course, you can always choose not to make new choices. In that case, any of the current choices will remain in their current state, whether that state is illegal or not.
If a spell has some rules or requirements about the choices made for it, those apply regardless of who controls that spell. For example, if a player plays a spell from face down, they must target game objects located at the battlefield the spell was played from unless the instructions of that spell indicate that a target must be chosen from some other location. Gaining control of such a spell doesn’t change this requirement when making new choices for the spell.
We’ll look at shaping up this section in a future rules update.
Ravenbloom Student’s triggered ability checks whether a spell that you control resolves. You gained control of the Stupefy, and it resolved, so you will have triggered Ravenbloom Student’s ability. Battering Ram and Legion, on the other hand, check whether cards were finalized . Although you gained control of Stupefy, you did not finalize it; you got it after it was already finalized by your opponent. Thus, your opponent’s Legion abilities will be active, and Battering Ram will only receive a [1] Energy discount.
Relevant Rules: 419.4., 419.4.a., 419.4.b.