Chained Rip-Spiral

Haste
Unstable {4} (When this spell is played, any player may pay {4} to counter it.)
Berserk {1}{r}{r} (When this creature attacks, you may pay its berserk cost to double its power. If you do, sacrifice it at end of turn.)
"It may be chained,
but I'll not be the one to slay it."