Big duck

Gentle giant  The duck will roll a d4 on the start of its turn if a 1 it cannot attack if a 2 it deals halved damage if a 3 or 4 roll as rules written.(can still perform bonus actions regardless of the roll)

True bond.  when the duck has bonded deeply with a player (as per the dm's choice) and the player is unconscious it gains immunity too charmed, deafened, exhaustion, stunned, freighted, petrified, restrained, grappled, and gains 1d10 health although it can only stand over the player and cannot move and will gain exhaustion after 50 rounds or until there are no enemies.(cancels gentle giant)

moving house. The duck can fly (120ft) swim (80ft) and takes halved movement penalty on difficult terrain.  the duck also gains plus 5 strength when carrying things having a carry weight of 992 lbs or pull weight of 1984 lbs (26+5=31x13=496x2=992) when at max carry weight or pull weight normal movement penalty applies. 

Quack. The duck makes an extremely loud quack that can be heard 80ft away make a con save 1d4 of damage and frightened.

Beak. Melee weapon attack +6 to hit  The duck stabs their opponents with its beak reach 15ft (2d6)pierce damage

Tidal wave. while in water the duck can use its feet to send a small tidal wave reach 30ft (1d4) bludgeoning damage

Intimidating stomp. to avoid conflict the duck will first try and intimidate its opponents by stomping reach 15ft (1d6) halved (if 1 damage is 1) con save frightend

Tidal wave. while in water the duck can use its feet to send a small tidal wave reach 30ft (1d4) bludgeoning damage

Beak. Melee weapon attack +6 to hit  The duck stabs their opponents with its beak reach 15ft (2d6)pierce damage