Each Tomnt is unique, with varying characteristics and power levels and each with their own name. Stats wise they are similar to the faerie dragon in the 5e mm. This leaves them at about a 2nd level cr with usually one spell slot and a low power attack. They are not evil creatures but definitely mischievous their modus operandi being to rewild further the feral lands.
Another defining characteristic of these creatures is that each one has a secret name which gives a person advantage over them. There may be a list of names somewhere tucked into an old book or under a shelf in a forgotten library which gives the names of some of them. Unfortunately though the list is in an undecipherable script from ancient times, even older than the fisheaters society.
Obeisances: shiny objects, meat, music, the colour red, fast motion, scary faces, milk, salt, bells, fire, alcohol
The following books contain information about Tomntoi:
Magus in The Hedgerows, contains information about Tomntoi names.
Mummers of the old Woods: contains information about Tomntoi obeisences.
Missives of a Salt merchant: contains information about their spell effects and temperament
Treatises on the root of two: contains a Rosetta Stone to transliterated the names found in Magus In the Hedgerows
Special attack, wild touch: when the Tomnt touches a creature at the base of the neck they may inflict "wild-mind" upon the creature. To successfully do this there is an opposed check (either strength v. Dex or whatever makes sense) to see if the touch is made and then a con save (cr 18) to see if the victim can resist the attack. If the Tomnt succeeds on its attack the victim animalizes over the course of several weeks until they become fully feral.