Evasion. If the skeleton is subjected to an effect that allows it to make a saving throw to take only half damage, it instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.
Magic Resistance. The skeleton has advantage on saving throws against spells and other magical effects.
Turn Immunity. The skeleton is immune to effects that turn undead.
Multiattack. The skeleton makes three scimitar attacks.
Scimitar. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit:15 (3d6 + 5) slashing damage.
In the Tomb of Horrors, treasure sometimes presents itself for the taking. In one such location, the "reward" for an attempt to grab some valuables turns out to be the animated skeleton of a giant—deadly not only because of its size and strength, but because it has defenses normally possessed only by undead of much greater power.