Resolute Watchdog

Most effects that grant indestructible are instants: they resolve, they do their job, and they cost you a card from hand. This one folds the protection into a permanent's sacrifice, so the fee is not a card at all but the body you spent to hold the ground in the first place. A defender wants to stay planted, yet its only proactive play is to remove itself, and that friction is what the design is built around. What the structure buys is a clean answer to targeted removal, a sweeper, or a losing combat exchange, delivered by a creature that was already earning its keep as a blocker. The indestructible lasts through end of turn, which covers the full combat step and any sorcery-speed board wipe an opponent queues up. Because the ability is instant-speed, it responds to a destroy effect already on the stack. As a permanent, of course, the watchdog is visible from the turn it lands: an opponent who reads the board plays around the sacrifice, baiting it out or holding removal for a turn when the mana is tapped. That readability is the tax you pay for an on-board trick, and the tacked onto the activation is the rest of it. You pay a small toll and surrender the wall, and the thing you actually care about lives.