Solro mage items
 

Do they work on all pets? if so what do they do?

https://wiki.project1999.com/Pet_Guide#Focus_Items has a short explanation.

They don't make your pets stronger unless you're a mage.

However, you can use them to cast Reclaim Energy on your pet, giving you back the mana you spent on it (in proportion to the pet's current HP). Not all pet-summoning classes get Reclaim Energy, so questing a mage focus item is the only way they can access that spell.

This does not, of course, work on charmed pets.

Also, technically only Mages can wield the items ... but all the other classes can still right-click them from inventory, to get the Reclaim Energy effect. This makes having at least one such item valuable for most pet classes..