I believe the rarest pet is the Europhious. Base pedigree of 75. Dopped by the last boss of Celestia. Gives 2 draconian polymorph cards and has spell proof pain giver unicorn and sprite
If your curious at the rarest hybrid, it's the Frost Hound (the 2 headed version of Orthrus + Collosus hybrid).
Rarest pet overall is the Sheep, only a handful of people selected by KI got one.
i agree with ya with sheep,only people who work for ki get 1 and random wizards. the seraph is not cause when im in the commons i see like 20 people with one
I'm not so sure about what the rarest pet actually is, but I am inclined to agree that it would be dropped by a boss in Celestia, or a higher level world.
Seraph is definitely not the rarest pet dropped in the spiral, but it is probably the rarest pet dropped in Wizard City.
The rarest drop is the storm hound from Malistaire, haven't seen a lot. The actual rarest pet inthe game is the sheep though, i think you need to work for kingsisle to have it
rarest pets are holiday pets and one-time-only event type pets, like storm beetle. the storm beetle was givien for the first million users who enrolled into ravenwood. It was available for "Play in November, Pet in Decmber" event, too.
To me a "rare" pet is only one that is retired. All the others can easily be hatched for to obtain. Pets such as the Pioneer Dragon, Danger Hound, and others which are retired are the ones that I consider as "rare." A pet that can be hatched for but is still often considered "rare" I believe is the Crimson Spectre obtained in through Pet Derby Tickets. Not many people have this as a pet. But besides that, there are not many others which are unretired yet considered "rare." I would definitely consider trying to get the spectre for your collection though!