Barbarian

Haste
Whenever this card destroys a creature or directly damages an opponent it gains 1 experience.
At 2,4,6,8,10 experience give this card a +1/+1 counters.
At 2 experience, give this card double strike. At 4 experience, this card becomes legendary. At 6 experience, give this card trample. At 8 experience counters, give this card three +1/+1 counters in addition to its first ability. At 10 experience, this creature becomes indestructible.