Tergrid, Lord of Fright

Signature {1}{g}{w}(As you cast this spell you may pay
the signature weapon cost, if you do copy this spell, the
copy enters the battlefield transformed)
When this creature dies, return it to its owner's
hand at the beginning of the next end step
Whenever a creature and opponent controls dies,
that player loses 1 life, then, if this is the first time
this ability has triggered this turn, exile it, for as
long as it remains exiled you may cast it and you
can spend mana as though it were m