Sarkhan, the Dragonspeaker

The +1 is the engineering trick the whole card orbits, and the load-bearing detail lives in the parenthetical: he keeps his loyalty while he is a creature. Most planeswalkers defend themselves by removing threats or spitting out chump blockers; this one defends itself by becoming the threat. Tick up, then swing the same turn as a 4/4 flier with haste and indestructible, surrendering no loyalty for the privilege. Timing is the point of the reversion: a sorcery-speed board wipe on your opponent's turn finds nothing to kill, since he is a planeswalker between your turns, and the indestructible clause covers his own combat, blunting damage-based removal and the wipe that catches him mid-attack. It is not a blanket shield, though: exile, bounce, sacrifice effects, and -X/-X shrinkage all still answer him during the creature window, so the "immortal Dragon" reads narrower than it sounds. The −3 is a clean four-damage removal mode for the turns you want to play goalie, folded into the same frame, and the −6 emblem is the rarely-cast finisher: a draw-two, discard-your-hand wheel that wants a curve low enough to empty fast. But the identity is the aggressive loop. Attack as a Dragon, lose no loyalty, repeat. He sits in the small lineage of planeswalkers built to be cast like creatures rather than run as engines, where the planeswalker chassis is mostly a more resilient delivery system for a recurring attacker. The price is the loyalty math each turn: the +1 and the −3 compete, so animating to attack means forgoing the four-damage shot.