These companions are large, fluffy, and love nothing more than cuddling by the fire. Though they can be disconcerting, having three heads to the usual one, they are far less volatile than their true Hydra counterparts - due mostly to the fact that only one head is ever awake at one time, with the other two tucked back into the enormous ruff of soft feathers that ring the bases of the necks. Their feathers are incredibly soft, and much sought-after for both beds and pillows as they retain a residue of the relaxing aura their previous owners exude on most occasions. Feathers are hard to get, however, as they cannot be pulled out - the companions moult once a year, which is the only time they take more after the hydra than the drake, During moulting season these companions are snappish and ill-tempered, and can send an unwary Magi to the healers with severe bites and clawmarks.
Four stubby wings covered in soft feathers protrude from the surface of this egg
These hatchlings will follow their Magi around crying plaintively until the Magi in question picks them up. They won't moult until they are adults, so these babies want to be carried 100% of the time. This leads to some sulking when they inevitably get too big to carried around by their Magi, and it isn't uncommon to find a Magi trying to persuade a sulking Feather Hydra to move from the corridor where it has installed itself and is now blocking traffic.
Having finally given up on having you hold it - now that it weighs more than 4x that you do - this companion is content to spend its days lolling around the keep in various patches of sunshine, or ferrying its Magi around. Though anyone can cuddle up, these companions are very much a one-Magi kind of pet and will not allow anyone else to ride it - and woe betide those who try
edit: LOOK AT WHAT LAUGHINGIDIOT DID