Sparring Regimen

An enchantment that turns every attack step into a growth-and-untap engine, which is a stranger design than the rate suggests. Untapping the creature it counters up is the wrinkle: it does not just make an attacker bigger, it keeps that attacker back to block on the crackback, so a single evasive body can grow every turn while still holding the fort. Pair the trigger with something that cares about being tapped or untapped (creatures with tap abilities, anything that wants to swing and still hold up interaction) and the untap clause stops being a footnote and starts being the point. The Learn on entry is the softener, letting the enchantment cash into a Lesson from the sideboard or loot away a dead card when the board is not ready for it, so a turn where the counter has nowhere useful to go still buys you a card. What holds it in check is the attack requirement itself: it does nothing on a stalled board, rewards you only for committing creatures to combat, and offers a single target per turn rather than a team-wide pump. That narrowness is the trade for an effect that compounds if left unanswered, an incremental value piece built around the idea that the same creature attacking turn after turn should be a threat that grows rather than a body that stops mattering.