Pets

Enabling old pet models
Enabling of the old pet models can be achieved either by entering configuration, or by making sure that this line exists in your eqclient.ini file

UseLuclinElementals=FALSE

Adoptable pets
Adoptable pets released so far include cats, large felines, dogs, and birds. Cat in a Bag, Big Cat in a Bag, Dog in a Crate, and  Bird in a Cage may be purchased in the Marketplace. Using the item will give you one of several different types, each at random.

They are familiars, not combat pets, and also do not offer any buff.

Selling
From the July 6, 2016 patch message:Lynea the pet collector in the Commonlands will purchase your excess adoptable pets for a unique currency. You can buy a random discontinued pet from her using this currency.

For selling her 10 adoptable pets, you get enough Adoption Coins to purchase one Random Pet in a Box.

Illusions
Since the November 16, 2016 patch, if you own the Familiar Key Ring feature, any illusion spells on summoned pets will persist when you zone.