Rune smasher

trample
{x}{x}{t}, put x rune counters on this creature.(a rune counter gives a creature hexproof until end of turn)
when this creature attacks, you must pay {u/b}{u/b}. when you do, remove all rune counters from this creature. it gets +x/+x untill end of turn where x is the number of rune counters removed in this way.