Monstrous Vortex

Discover was built to reward casting big spells, and this enchantment turns that reward into a compounding loop by scaling the trigger to the very thing that powers it: cast a fat creature, dig for something roughly its size, and the free spell you flip is likely another fat creature that fires the enchantment again. The power-5-or-greater gate matters because it makes this a payoff specifically for the top of a green curve rather than generic card advantage on every mana dork and utility creature; it pays out in cards priced to match whatever you just resolved. A five-drop hits discover 5, an eight-drop hits discover 8, so the ceiling of the effect rises with the ceiling of your deck rather than sitting at a fixed value the way most enchantment engines do. That coupling is the clever part. The randomness of discover is the tax on all this: you exile off the top until you find the first nonland card at or under the number, then either cast it for free or tuck it into hand, and the rest goes to the bottom in random order. You cannot reliably chain it, and a deck too heavy on lands and cheap fixing dilutes the hit. Its natural habitat is a deck stacked with expensive threats, where every payoff you flip is itself a payoff-trigger, and the enchantment stops being an engine and starts being a snowball.