Take Up the Shield

The counter is the tell. Most combat tricks in white's protection lineage buy you a turn and vanish: fogs, one-shot indestructible spells, temporary regeneration effects that leave the creature exactly where it started. Here the reactive package (lifelink to swing the life total back your way, indestructible to shrug off lethal damage or any "destroy" clause) rides on top of a permanent +1/+1 counter that stays after the fight is over. That single addition changes the card's math. A pure protection spell is a break-even proposition; you spend a card to keep a card. This one leaves growth behind, so surviving the block also means winning the exchange and keeping the bigger body. Instant speed is what lets the whole thing operate on your terms: you hold it until the opponent has committed to a block or aimed removal at your creature, then answer the play they already made while the counter locks in regardless of how the combat resolves. It presents as defense, but the durable stat bump quietly pulls it toward aggression, and that dual nature (a two-mana trick that both saves and permanently improves the thing it saves) is the whole reason to run it over a plainer pump.