Tiberium wildlife

There were two varieties of Tiberium creature that were present during the Second Tiberium War, the Visceroid and the Fiend. The Visceroid was further subdivided into two types, Adult and Baby visceroids.

Baby Visceroid
When a regular human infantry received too much Tiberium saturation in his blood, he converted into a baby visceroids. Although decently resiliant, especially against infantry, baby visceroids were incapable of attacking. They basically wandered the Tiberium fields and patches until they found another baby visceroid, at which point they would transform into an adult visceroid.

Baby visceroids looked like moving pools of some strange and fluid liquid, wandering the battlefield. They healed themselves very quickly in Tiberium Fields, but as units, were hampered by a lack of attack.

Adult Visceroid
Adult Visceroids were very capable of attack, however. When two baby visceroids joined together, the demeanor or personality of the Visceroid changed. Not only was the adult visceroid more resiliant and still able to heal in Tiberium, but it was capable of swallowing a non-cyborg infantry unit in one hit. It was also effective against vehicles, more than a match for a single Titan Walker. Further, its speed allowed it to retreat to a Tiberium Field when it was damaged.

Tiberium Fiend
Fiends looked like giant dogs, or perhaps, a cross between an elephant and a dog, with Tiberium crystals running down its back. It could actually attack by flinging some of the Tiberium shards on its back at its enemies, causing heavy damage to vehicles, structures, and infantry, although more heavier vehicles were more difficult to kill. The Fiend was unique among Tiberium Creatures in that it had a ranged attack. However, like all other Tiberium creatures, the Fiend could heal in Tiberium.

Floater
Floaters began to grow more and more prevalent as time went on, and the first phase of the Second Tiberium War drew to a close. Floaters hovered over the battlefield, releasing clouds of Tiberium Gas behind them, which made them very effective against infantry - they could potentially turn infantry into baby visceroids with the gas it released. Furthermore, the floaters' electric attack, which it could use when in contact with the target, was extremely effective against both vehicles and structures. The floater could even stop the vehicle it was attacking to fire.

Usage
The first recorded 'usage' of Tiberium Creatures was by the forgotten. As they attempted to rescue their leader Tratos, they saved a Tiberium Fiend from some Nod soldiers - in gratitude, the creature assisted them in rescuing Tratos, but eventually threw itself against the Nod defenses and was destroyed.

The second usage was of a pack of Tiberium Fiends. As a last ditch measure, the main mutant base containing what Cabal believed to be the Tacitus unleashed a number of Tiberium Fiends, but they were cut down by the powerful Nod forces present in the area.

Finally, Cabal managed to control Tiberium Creatures, by having drugged units lure them out from the Genesis Pit. From there, the creatures would attack anything they saw, including GDI forces. Cabal used Tiberium creatures at least twice: First was to destroy a GDI outpost and numerous civilians from the area immediately surrounding the Genesis Pit. The second use was in his attack on a similar outpost - but with far larger forces and civilians in the area.

Counters
Firstly, Tiberium creatures were very vulnerable to railguns and other high powered weapons such as the Cyborg Commando's plasma weapon. These powerful weapons could destroy all Tiberium Creatures in a single hit. Furthermore, anti-tank weapons were effective against all types of Tiberium Creatures; in groups of 5 or more, Titan Walkers or Tick Tanks could easily destroy Tiberium Creatures.