Knollspine Invocation

The activation cost is a perfect double payment: you announce X in mana, then discard a card whose mana value is exactly X, and the enchantment deals X damage to any target. That strict equivalence is the whole engine. You pay full price twice over, once in mana and once in card advantage, to convert a card's mana value directly into damage you can point at a creature, a planeswalker, or a face. Most repeatable burn scales with land count alone; here the ceiling is set jointly by your available mana and the heaviest card you can afford to throw away. To fire a seven-point shot you must both have seven mana untapped and a seven-drop you are willing to discard. The constraint cuts both ways: a cheap hand cannot inflate its damage, and a top-heavy hand cannot spend its fat cards for free. What it rewards is a deck that treats expensive cards as ammunition rather than as plays, where a clogged grip or an uncastable bomb stops being a liability and becomes a stockpiled shell. The instant-speed timing matters: when you are holding unused mana and dead cards, you can route both into a removal shot or a kill, turning waste on two axes into a single coordinated activation. The deckbuilding question it poses is not how much mana you have but how expensive your hand is allowed to get.