Spellhound

Arcane Sense. The spellhound can pinpoint, by scent, the location of spellcasters within 60 feet of it.

Channel Breaker. The spellhound has advantage on attack rolls against a creature, if the creature is concentrating on a spell.

Keen Hearing and Smell. The spellhound has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Magic Resistance. The spellhound has advantage on saving throws against spells and other magical effects.

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.