Cavern of Stolen Wishes

When this land enters the battlefield, put 3 wish counters on it. When it has no wish counters on it, sacrifice it.
{t}: Exile target creature you control. Add X mana of any color to your mana pool where X is the amount of wish counters on this land times 2. If you exile a Djinn creature, X equals the amount of wish counters on this land times 3 instead.
At the beginning of your upkeep remove a wish counter from this permanent.