They were shaped by the Shapers to provide meat for the population. They are one of the few types of creation that are enabled to reproduce naturally.
There may be more to the Ornk than meets the eye. A herd of Ornk on Sucia Island appeared to develop a limited form of intelligence, although they had also become physically unstable. These Ornk would explode upon death, and had established a primitive religious cult worshipping an entity known as the Ornk Lord. Whether these developments resulted from centuries of neglect by Shapers, or from complications similar to those that created Heustess, is unknown. In Geneforge 5, there is also a special ornk that is intellegent that you must kill. If you can find this ornk among a few others in the swamps to the east of the Mera-Tev, than you can talk to it before you fight it.
Often, they can be seen being taken care by Serviles out in the fields. Killing ornks does not immediately get most towns to attack, although gets them more annoyed than stealing items. An ornk yields between 1 and 3 pieces of meat.
Variations exist, such as the Oozebeast and the Uberoozebeast.
The 'Create Ornk' canister is an Easter Egg in all Geneforge versions. Player created Ornks are treated as Battle Shaping creations for purposes of calculating level, but a player can create Ornks even with no Battle Shaping.
In battle, Ornks are quite weak. They can perform melee attacks with their tusks, but move much slower than other creations and humans, making it difficult to move within melee range.