Clockwork Owlbear Berserker

Clockwork Synergy. This clockwork creature always knows its masters next move and takes its turn immediately after its creator

Ultimate Clockwork Overdrive. The Owlbear can overload its gears and core growing to huge size and deal an addition (1d10) damage on all attacks but drops its AC to 14.

Multiattack The owlbear can attack using maul three times per turn while in overdrive

Maul. Melee Attack: +14 to hit, reach 5 ft., 1 target. Hit: 14 (1d10 + 8) slashing damage. 

Slamming Jump.  The Owlbear 30 ft. leaps into the air and lands, any creature within 20 ft. of its landing makes a DC 20 Dexterity save or takes target. Hit: 18 (4d8) bludgeoning damage. 

Owl Wrath. Once per day the owlbear can make a wrathful fury of attacks against one creature but becomes stunned for a turn after attacking this way. Melee Attack: +14 to hit, reach 5 ft., 1 target. Hit: 51 (6d10 + 18) slashing damage.