Melbhal, Shambling Pumpkin

Sunburst (This enters the battlefield with a (+1/+1 or charge) counter on it for each color of mana spent to cast it.)
{w}{u}{b}{r}{g}: Until your next upkeep, whenever you cast an artifact creature, it gains sunburst.
If Melbhal, Shambling Pumpkin would be destroyed while it has a +1/+1 counter on it, regenerate it and remove a +1/+1 counter from it instead.