Foot of the Elephant

Menace, Deathtouch, Trample
For every human creature, reduce the mana cost
by {1}.
Whenever damage would be dealt to this creature
by a radioactive source, gain a +1/+1 counter
equal to the amount of damage instead. At the
end of every turn, all other creatures gain a -1/-1 counter.
If a creature has gained a total of 5 -1/-1 counters,
regardless of all other effects, exile that creature.