Passive buffs: armor plating, high tension springs, flame spout, extra attack.
Clockwork brain: greater INT, can use magical items that you've infused, and can be infused directly which allows it to cast those spells.
Magic-imbued strikes: Tustm's attacks count as magical for the purposes of overcoming resistance.
Defensive Response: if you are attacked and the attacker is within 5 ft of Tustm, it can make a single melee attack against your attacker as a reaction.
Multiattack: Tustm makes two hooves attacks or two gore attacks.
Hooves. Melee weapon attack, range 5 ft. +8 to hit, 1d8+4 bludgeoning damage
Gore. Melee weapon attack, range 5 ft. +8 to hit, 1d6+4 piercing damage.
Flame Spout: blast of fire in a 5ft wide 60 ft long line, requires all creatures in it to make a DC 15 dex save or take 10d6 fire damage. Once per short or long rest.