Pair him with the decks enters the battlefield Villains and youve got a snowball that refills your hand and your board in the same swing
It would be sweet if it gave 1/-1 in the form of counters though, but dont be fooled
If you choose not to cast the copy, or you can't cast it (perhaps because there are no legal targets available), the copy will cease to exist the next time state-based actions are performed
Other than that, Doors of Durin can show a nice time if you play Red and Green where it bypasses the Summoning Sickness, helps you put a creature from your hand to the battlefield, tapped and attacking
This card costs four mana, is instant and has bargain, which means you can sacrifice an artifact, enchantment or token as you cast it for a better effect
Mana elves that tap for green mana often charge less than $1 per copy