Metallurgeon

Regeneration spent most of its life as a creature's defense against burn and combat trades, but here it gets pointed at an entirely different target class. The shield protects artifacts: equipment, mana rocks, the permanents that hold an artifact deck together, all of which are exactly the cards opposing decks try to pick off with destruction effects rather than damage. That redirect is the whole idea. A repeatable regeneration source asks one white mana per activation, so the protection is real but rationed: you cannot blanket-shield a board, you choose what survives. And because the artificer is itself an artifact creature, it is a legal target for its own ability, capable of tapping to save itself the same way it saves a mana rock (though spending the activation on its own 1/2 body usually means a more valuable artifact goes unprotected). The effect captures a moment when regeneration was being repurposed to defend the things players were investing mana into building, not just the bodies they sent into the red zone. It rewards a deck dense enough in artifacts that one creature's tap is worth a turn's attention; in anything lighter, the activation simply has nothing worth its while.