Multiattack

The spellhound makes two bite attacks.

Bite

Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) piercing damage. If the target is a creature, it must succeed on a DC 14 Strength saving throw or be knocked prone.

Nullifying Howl (1/Day)

The spellhound lets out a high-pitched, multiphonic howl to disrupt magical effects within 60 feet of it. Any spell of 3rd level or lower within the area ends. For each spell of 4th-level or higher in the area, the spellhound makes an ability check, adding its Constitution modifier to the roll. The DC equals 10 + the spell's level. On a success, the spell ends. In addition, each spellcaster within 30 feet of the spellhound that can hear the howl must succeed on a DC 14 Constitution saving throw or be stunned until the end of its next turn.