Quick ruling question: I've got a friend who insists that Celestial Mantle and Sanguine Bond can't make a combo because lifegain and doubling a controller's life are two different effects.
Is that true? I was under the impression that doubling a controller's life is basically just adding their current total to their health as a lifegain.
C.R. 701.9d says that doubling a player's life total means "gain[ing] or los[ing] an amount of life such that [the player's] new life total is twice its current value". Thus, in general, if a player whose life total is 10 doubles their life total, that player gains enough life to go to 20 life, so 10 life. (Note that the rule also speaks of "los[ing]" life because in rare cases, a player can have a negative life total by the time their life total is doubled [see also C.R. 107.1b].)
Is that true? I was under the impression that doubling a controller's life is basically just adding their current total to their health as a lifegain.