This is looking at what appears to be a somewhat bizarre rules exploit, and attempting to determine if it is, in fact, viable under the rules.
Premise: We have a Bard who likes having friends – a lot of friends. He has Find Familiar. At level 10, he takes Find Steed and Find Greater Steed as his magical secrets and the DM has given him a ring of Spell storing.
Now, it’s pretty clear that by himself, he can have one Familiar, one Greater Steed, and one Steed (perhaps a mastiff, because he wants a dog, and can’t ride two things at once). We’ll say that he chooses a hawk as his familiar.
Can the bard allow the creatures summoned by the spells to attune to and use the ring of spell storing containing Find/Familiar spells to summon Steeds/Familiars of their own?
A DM might adjudicate that a hawk/mastiff/griffin has no fingers and cannot use a ring, but Polymorph is available to a Bard of that level, and seems like it should be able to handle the issue for the Steed and Greater Steed. (I’m not sure if there are any beasts of low enough CR for the familiar that would have something appropriately finger-like.)
Is there a reason why the dog would not be able to have a perfectly loyal griffin of its own? Is there any real limit to the potential pyramid of perfect loyalty/obedience that would result?
This is in some ways similar to the linked question, and may have the same answer, but it is distinct on a couple of points. The first is that the linked question is about the Pact of the Chain familiar, most of which have obvious fingers already, as compared to the generic Familiar, Steed, and Greater Steed. The second is that this question is specifically about the three Find spells, which seem like they might be a special case – it’s not merely about whether your dog (polymorphed into an octopus/monkey/whatever) is able to cast the spell, but whether they are able to permanently maintain the found creature afterwards. In particular, this seems to severely break the intended limit of one steed, greater steed, and familiar per PC, and it seemed like there might be some further limit in place preventing it from working out this way.