Undertitan

369.1. A Replacement Effect can usually be identified by the presence of the terms "as," "would," or "instead." Example: Zhonya's Hourglass reads "The next time a friendly unit would die, kill this instead. Heal that unit, exhaust it, and recall it." This is a replacement effect that alters the execution of any Game Effect that would kill a friendly unit. Example: Undertitan is a unit that reads in part "As I'm revealed from your deck, [Add] [2]." This is a replacement effect that alters the execution of any Game Effect that reveals Undertitan from your deck.

370.1.b.1. In the case of Replacement Effects that describe a game action to occur "as" an event occurs, the described event is replaced by that same event plus the game action being performed. Example: Undertitan is a unit that reads in part "As I'm revealed from your deck, [Add] [2]." The event of Undertitan being revealed from your deck is replaced by Undertitan being revealed from your deck and adding [2] Energy to your Rune Pool.