Arwen, Mortal Queen

The indestructible counter is the whole engine, and the design turns a static keyword into a one-shot resource. Most protective effects hand out indestructibility as a passive shield; here it arrives as a single consumable token she removes from herself to shield another creature, then converts that spent defense into permanent stats: a +1/+1 counter and a lifelink counter on the target, and the same pair on Arwen herself. That trade is the elegant part. She enters with exactly one indestructible counter and has no way to make more, so the shield is a single decisive gift rather than a loop, and the whole ability fires once unless something outside her replenishes the resource. What that scarcity buys is a clean decision at a single crux: which creature deserves the one-turn shield, given that both it and Arwen grow together no matter what. The lifelink counter matters as a keyword you either have or don't (a second one is redundant), so the value is not in stacking drains but in permanently welding lifegain onto two bodies that didn't have it. Point the ability at an evasive threat and you have turned a defensive keyword into an attacker that races and gains life at once, while Arwen banks the same growth alongside it. Read as a design object, she is a conversion machine that spends protection to buy stats and lifelink across two creatures, and the tension is that the trade only happens the one time.