If I use Ravenborn Tome and play Hextech Ray, then my opponent uses Mystic Reversal to gain control of Hextech Ray, how much damage does the spell do?

Ruling: When your opponent takes control of Hextech Ray with Mystic Reversal, they become the controller and are considered to be playing the spell. Since they don't control Ravenborn Tome, the spell does regular damage (not the boosted damage from Tome).

Nuances:

• "Playing" a spell means properly resolving it without it being countered
• The "you" in Ravenborn Tome refers to the controller of the Tome
• When a spell changes control, the new controller is the one "playing" it for the purposes of card effects