Knight of the Holy Nimbus

The joke is that you don't decide when this Knight dies: your opponent does. Built-in regeneration on a two-drop shrugs off burn and combat damage, surviving anything that would destroy it. But the design pays for that resilience with the strangest activation clause in the game, an ability only the controller's opponents may use, that switches the regeneration shield off for the turn. So the Knight is functionally invincible against decks unwilling or unable to spend the two extra mana, and a fragile 2/2 against anyone who reads the card and pays the toll. Note the gap regeneration leaves open: it replaces destruction, so it does nothing against sacrifice effects and edicts, which remove the creature without ever trying to destroy it. Flanking sharpens the trap from the other side of combat. When the Knight attacks and a defender without flanking blocks, that blocker eats -1/-1, so the opponent has to weigh paying two mana to shut off regeneration on a creature their own blocker is already shrinking. It is asymmetry-as-flavor, a power level that polices itself depending on whether the opponent knows the answer is sitting in their own hands. Most regenerators ask their controller to hold up mana; this one hands the off-switch to the enemy and dares them to find it.