Sting. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 2 (1d4) piercing damage. Additionally, if the sunfly is on an Outer Plane, it injects the target with a toxin, the effect of which is determined by the sunfly's location:

Upper Plane. The target sheds bright light in a 5-foot radius until the end of its next turn.

Neutral Plane. If the target is concentrating on a spell or similar effect, it makes the Constitution saving throw with disadvantage to maintain its concentration.

Lower Plane. The target's speed is reduced by 5 feet until the end of its next turn.

Illumination. The sunfly sheds bright light in a 5-foot radius and dim light for an additional 5 feet, or it uses a bonus action to extinguish the light.