Unholy Annex // Ritual Chamber
The front half draws you a card each turn, and the clause riding on that draw is what splits the design in two directions. Control a Demon and each of your end steps drains two life from each opponent while topping you back up; control none and the same trigger costs you two life instead. That binary is the whole engine. Most black card-draw enchantments charge a flat life tax on the Phyrexian Arena template; this one hands you a lever, converting the tax into a payout the moment a Demon hits the board. The Ritual Chamber door is the built-in answer to its own drawback, unlocking a 6/6 black flying Demon token that flips the life swing in your favor. But the two doors cost mana independently, so you rarely open both cheaply, and the front half often runs solo for a turn or two while you eat the two-life bill. The elegant part is that the Demon requirement is agnostic about source: any Demon you control satisfies it, not just this card's token. So the enchantment plugs into a Demon shell as a standing payoff and stays self-contained outside one, unlocking its own answer when it has to. It rewards a board you were already building toward rather than demanding a dedicated combo, and the drain scales with how long you keep a Demon standing.
