One of the most desired symbiotes in the known world is the Neuronimal. Extremely rare, the symbiote can be found attached to various types of helmets and looks like a set of roots that form the chinstrap. Inside of the helmet is a set of neural detectors that can determine whether or not brain activity is close enough for assimilation. When there is no activity nearby, the symbiote lays dormant and enters a state very similar to coma. The only functions running are the brain wave detectors.
When the helmet is put on, the detectors immediately determine the status of the brain and whether or not it is a functioning brain or not. If it is, the roots forming the chinstrap immediately burrow into the neck and work their way to the brain stem. There is no pain since some of the tendrils provide anesthesia to the central brain region. At this time, the symbiote starts feeding on the fluids produced by the brain during activity.
The primary benefit of this symbiotic relationship is significantly increased mental awareness and mental acuity. The older the symbiote, the more intelligent that the host becomes. He is able to remember more information, notice more minute details and work out problems significantly faster than before.
At some point, though, the host realizes that this is not a long-term solution. Due to the increased activity on the brain, it seems to decay faster than normal. Eventually, the level of intelligence becomes normal due to the advance decay of the brain. This may happen with days or months of when the symbiote is attached.
The hosts of the symbiote seem to act as they normally would but exhibit much more mental capacity. When the helmet is first put on, the host will go through a period where they are arrogant and head-strong (if they weren’t already fairly intelligent). Eventually, due to their nature, they tend to start taking up activities that mean a great deal to them and have very little time for other people.
Depending on the nature of the combat, most hosts with Neuranimals tend to be extremely good at adapting the current situation for a favorable outcome. This is either through the use of make advanced weapons from the simple items around them to talking and convincing others that combat is not the way.
For those who are mages, they have a wide array of spells that are available to them. Also, more of an understanding of the basic way that magic works help them create new spells that no-one had ever encountered.