Regret This In The Nothingness

Deal X damage to X tapped creatures. If X
is 4 or more this gains Split Second & the
damage dealt this way is unavoidable. If
destroyed it cannot be Regenerated.
You may spend X life to add {x} mana that
can only be used to cast or equip artifacts.
If X if 4 or more then you don't lose the
unspent mana as steps & phases end.