Fauna of the Darklands

The Darklands are mostly known for their corruptions, but there are also un-tainted descendent of the beasts bred by the Dark Lords. In addition to the dire wolves and wargs that work in partnership with the orcs, the feral descendants of the keeper's prize stock live wild. Known as Dark Wolves, they are taller and heavier even than dire wolves, and as fiercely intelligent as any warg. Unlike their kin, the great wolves seldom allow themselves to be ridden, but they only attack livestock if starving, and sometimes form partnerships with the druids and rangers of the Woodcutters.
The Dire Swine of the southern marshes are less intelligent, mere animals, but possess a stubborn speed and power that makes them excellent beasts of mount or burden, albeit truculent and demanding ones. They lack the pace of horses, but their endurance is peerless, and a tough hide and gouging tusks make them brutal in battle.
In the great roosting caves which look out from the Great Shield range above the Darklands - especially on the outskirts of the city of Nighthall - the Great Bats rest. The descendents of the war bats of the Legions, these creatures are large and strong enough to carry an armed and (lightly) armoured orc into battle, and many of them still do; the Kingsguard of Nighthall are still mostly air cavalry. Swift and agile, and with an almost overwhelming advantage in night operations, they are treasured allies.
Also originating in the Great Shield, the vixir have gone everywhere the ore diasporas have gone, as pets and rat- catchers, leading to feral populations. Small, vulpine omnivores with leathery, bat-like wings, they thrive in almost all environments, with the exception of those areas where a tressym population is established. Although either species will defend their 'territory from the other fiercely, when introduced to an area together they seem to form partnerships, and even what seem to be mating - if not breeding, due to genetic differences - pairs. Vyxir are popular familiars for orc spellcasters.