Theriomythic can be used by individuals who straddle the Otherkin and Therian communities, in that they identify (non-physically) as one or more mythical type creatures (IE. Dragon, griffon, etc.).   This term is used by people who feel that their theriotype/kintype is more wild and instinctual or a being that does not have what is considered an advanced culture (i.e. a dragon or unicorn that does not speak a language and that does not use magic). These individuals may feel more at home in the Therian community or find it easier to discuss their more feral experiences and shifts with Therianthropes.
The term seems to have been originally coined on the Therian Wilderness Forum in 2010 as theriomythos.  It was then translated into Spanish as los theriomitos by Otherkin Hispano.  It was re-translated from the Spanish into English as theriomythics by Akhila, on May 24, 2013. 
So, apparently the term, “theriomythic” isn’t exactly a new concept in the therian community though one that didn't gain a lot of attention. More the new term, theriomythic, is people coming to a similar conclusion and use of phrase as others had once perhaps.  - LionGoatSnake (aka House of Chimeras)A forum called "Betwixt and Between" was created by Arawn in 2013. This forum was specifically for theriomythics, but it never saw a lot of activity. It is now defunct, and while there are a couple snapshots from the Wayback Machine, they don't give us much more information.
- ↑ AnOtherWiki (accessed Sept 2 2017) https://anotherwiki.org/wiki/Theriomythic
- ↑ Feral Nature (accessed Sept 2 2017) http://feralnature.forumotion.com/t83-therian-otherkin-terminlology
- ↑ Re Harakhti, May 28, 2010 http://therian-wilderness.proboards.com/thread/3082/common-misconceptions-faq (accessed Sept 2, 2017) Archived at http://archive.is/2PihD
- ↑ http://archive.is/jEmgm (accessed Sept 2, 2017)
- ↑ http://liminalbeast.tumblr.com/post/43897395257/theriomythics (accessed Sept 2, 2017) Archived at http://archive.is/ZnS5u
- ↑ Jarandhel, Theriomythics, Tumblr, February 28, 2013, https://jarandhel.tumblr.com/post/44222181640/theriomythics (accessed April 4, 2018)
- ↑ Golden Spirit, "Classes or Types", Otherkin Hispano, https://sites.google.com/site/otherkinhispano/tipos (access April 4, 2018) Archived at https://web.archive.org/web/20180404235637/https://sites.google.com/site/otherkinhispano/tipos
- ↑ https://groups.google.com/forum/#!topic/alt.horror.werewolves/dHQRGjrNv9U Archived at https://archive.is/cqBgi
- ↑ http://liongoatsnake.tumblr.com/post/100418903000/a-kin-history-tidbit-weremythic Archived at https://archive.is/NxcNh
- ↑ Betwixt and Between archived page (accessed May 25 2018) https://web.archive.org/web/20130820014912/http://betwixtandbetween.lefora.com/