Thalia, Heretic Cathar

The whole design lives in the word "enter." Tapping an opponent's creatures and nonbasic lands as they hit the battlefield is not a one-time hit like a mass-bounce or a stun counter; it is a standing tax on two specific things they keep needing to do. A creature cast on their turn cannot block until it untaps, so it sits there as a free attack for you. A nonbasic land they fetch or play comes in untapped no longer, costing them a turn of development every time they want to build out their mana. The effect ignores artifacts, enchantments, planeswalkers, and basic lands entirely, which sharpens rather than dulls it: it targets exactly the two permanent types that decide combat and tempo. Against a manabase leaning on fetchlands, shocklands, or any greedy nonbasic, the friction is constant rather than occasional, and each thing the opponent does lands one beat behind. The 3/2 first-striking body is what makes the tax cash out, turning "your blockers are tapped" into reliable damage instead of a stalled board. This is a different creature from the spell-taxing Thalia, Guardian of Thraben: where that one slows what opponents cast, this one slows what opponents do once it resolves, attacking the untap step instead of the stack. It belongs to a narrow white lineage that wins by making every opposing action slightly worse, content to grind an opponent half a step behind for ten turns rather than answer any single threat.