Barrel of Radioactive Liquid

Barrel of Radioactive Liquid enters the battlefield
with 1 radiation counter on it for each color of
mana you spent to cast it.
{1}{t}:Put a radiation counter on Barrel of Radioactive Liquid.
{3}{t}:Sacrifice Barrel of Radioactive Liquid.
When Barrel of Radioactive Liquid leaves the battlefield, it deals X damage divided equally to
any number of target creatures, where X is the
number of radiation counters on it.