Yasharn, Implacable Earth

The static ability is a flat prohibition, not a tax and not a counter: players simply cannot pay life or sacrifice nonland permanents to cast spells or activate abilities. That single line reads on an enormous slice of combo and value machinery. Life payment and sacrifice fodder underpin aristocrats loops, fetchland-fueled manabases, Phyrexian mana, and the graveyard-recursion engines that feed creatures to an outlet, and this shuts all of it off at once. Unlike a tax, there is no paying around it; the play cannot be made while the boar sits on the board. The lock is symmetric, reading on both players' resources equally, which is why it lands hardest for a strategy that already sidesteps its own life-and-sacrifice costs while an opponent's engine seizes up. In spirit it answers a play pattern rather than a card, closer to a permanent that hates on a mechanic than to any single hatebear. The enters trigger is what stops it from being pure interference: digging up a basic Forest and a basic Plains and shipping both to hand is fixing plus a card of raw advantage, so the 4/4 body advances your own plan instead of just wrenching the opponent's. The two clauses pull opposite directions. The fetch rewards casting it early for the mana; the lock wants it landing at the precise moment an opposing engine is about to fire. Resolving that tension in sequencing is the whole game with this card.