Air Guard

Climber.  Climbing no longer costs the air guard extra movement, and when it makes a running jump, the distance it can cover increases by 5 feet.

Evasion. If the air guard is subjected to an effect that allows it to make a Dexterity saving throw to take only half damage, the air guard instead takes no damage if it succeeds on the saving throw, and only half damage if it fails. 

Sneak Attack.  Once per turn, the air guard deals an extra 14 (4d6) damage when it hits a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 feet of an ally of the air guard that isn't incapacitated and the air guard doesn't have disadvantage on the attack roll.

Unending Breath. The air guard can hold its breath indefinitely while it's not incapacitated.

Wind Magic. The air guard spellcasting ability is Constitution (spell save DC 15). The air guard can innately cast the following spells, requiring no material components:

1/day: levitate

Dagger. Ranged Weapon Attack: +8 to hit, range 20 ft./60 ft., one target. Hit: 7 (1d4 + 5) piercing damage and 3 (1d6) thunder damage.

Light Crossbow. Ranged Weapon Attack: +8 to hit, range 80 ft./320 ft., one target. Hit: 9 (1d8 + 5) piercing damage and 3 (1d6) thunder damage.

Shortbow. Ranged Weapon Attack: +8 to hit, range 80 ft./320 ft., one target. Hit: 8 (1d6 + 5) piercing damage and 3 (1d6) thunder damage.

Shortsword. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 8 (1d6 + 5) piercing damage and 3 (1d6) thunder damage. 

Uncanny Dodge. When an attacker that the air guard can see hits it with an attack, the air guard can use its reaction to halve the attack’s damage against it.