You gain life equal to the damage dealt to you this turn. Simulacrum deals damage to target creature you control equal to the damage dealt to you this turn.
10/4/2004 You can’t use Simulacrum on Loss of Life, just damage.
10/4/2004 This is not damage prevention or redirection. It actually is life gain and newly dealt damage.
8/1/2008 Simulacrum is the source of the damage. If an effect needs to know a characteristic of the damage’s source (Protection from Black, for instance), it will see the damage coming from Simulacrum.