Multiattack. The death dog makes two Bite attacks.

Bite. m +4, reach 5 ft. Hit: 4 (1d4 + 2) Piercing damage. If the target is a creature, it is subjected to the following effect. con DC 12. 1 The target has the Poisoned condition. While Poisoned, the target's Hit Point maximum doesn't return to normal when finishing a Long Rest, and it repeats the save every 24 hours that elapse, ending the effect on itself on a success. Subsequent Failures: The Poisoned target's Hit Point maximum decreases by 5 (1d10).