Karthol, Dreaded Slavelord

Whenever you would lose life, you may sacrifice
any number of creatures to reduce the amount of
life you lose by an amount equal to the total
toughness of the creatures sacrificed in this way.
(To a minimum of 0)
{u/b}{u/b}{t}: Return target creature from any graveyard
to the battlefield under your control as a hostage.
(Hostages cannot attack, block and lose all abilities)