Great Sable Stag
A piece of pure hate dressed as a vanilla beater. The 3/3 body and the green mana cost are almost beside the point: what this Elk is built to do is be miserable for two specific colors to answer. Protection from blue and from black turns away the toolkit those colors bring against a green attacker (Doom Blade and its cousins, Mind Control effects, blockers, the targeted bounce that resets tempo), all of it bouncing off. The uncounterable clause shuts the last door: blue cannot stop it on the stack, so it resolves no matter what permission the opponent is holding. Stack those two restrictions together and you have a creature that lands in play and demands a board-based answer from precisely the two colors least inclined to fight on the ground.
That is the whole design logic: not a generically good creature, but a wall raised against half the color pie. Against red, white, or a green mirror it is a 3/3 for three with no relevant text. The interesting wrinkle is that protection is doing double duty here, granting evasion (it can't be blocked by blue or black creatures) and immunity (it can't be killed or stolen by them) inside a single keyword. It is a clean illustration of how narrow a hosing card can be while still warping a matchup the moment it is correctly pointed.
