Multiattack

The oasis keeper makes two attacks: one with its stinger and one with its bite

Bite

Melee Weapon Attack: +9 to hit, reach 10 ft, one target. Hit: 21 (3d10 + 5) piercing damage.

Stinger

Melee Weapon Attack: +9 to hit, reach 10 ft, one target. Hit: 14 (2d8 + 5) piercing damage, and the target must make a DC 15 Constitution saving throw. On a failure, the target takes 14 (4d6) poison damage and is incapacitated for 1 minute. On a success, the target takes half the damage and isn't incapacitated. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.