The Gnarl is a creature of the forest like no other. Away from the walls of New Sheoth, they are called the Walking Trees. Gnarl are known for their affinity with the elements. If a Gnarl is struck by elemental forces of fire, frost, or shock, it uses that energy to grow stronger and larger. Fortunately, this effect only lasts for a short time.
It is the will of Sheogorath that the Gnarl confuse and bewilder the unwary mage. To that end, it gains resistance to the element it is struck with, but becomes weaker to the other two. The wily mage will quickly switch between elemental spells to take advantage of this. Lesser wizards will suffer if they continue to use the same spell over and over.
In recent years there have been rumors of smiths that are able to use the amber sap extracted from Gnarl to make sturdy armor and weapons. As of yet, this gossip has not been confirmed.
More is not known about the Gnarl than is known. No-one has been able to determine the gender of Gnarl, or if they even have them. Young or immature Gnarl have never been seen. One academic suggested that Gnarl are born full-formed from trees that are struck by lightning. This absurd suggestion has not been confirmed.
Similarly, we have no knowledge of their diet or social habits. Presumably they feed directly from the sun and earth, like trees do. There are no reported cases of them communicating, even among each other. However, they do seem to have a truce of sorts with other woodland creatures such as the Baliwog and Elytra.