Eldrigender is a gender, or possible lack thereof, defined as dark, nebulous and ultimately unknowable. The term is similar to gendervoid and agender in lack of gender, but is different to these terms because it isn't inherently genderless.
Eldrigender was coined on February 26th, 2019 by mogai-archive on Tumblr.
The flags were created by eldrichtrender on tumblr on June 10th 2019. The color meanings are as follows: Dark blue represents the "dark" part of the identity, as well as the depths of the ocean. Silver represents the ambiguity or possible lack of gender, purple represents a nonbinary identity as well as deep space, light gold represents ancient arcane secrets and the identity's unknowable nature and blue-dark green represents it's connection to the void, spaces between realms and things that should not be viewed by mortal eyes.
The alternate versions feature elder signs in the middle, a fictional part of the Cthulhu Mythos by H.P Lovecraft. An elder sign is a symbol that protects the bearer by attack from mythos-related creatures. 
- Eldrigender (reblog + archive)
- https://web.archive.org/web/20200519100722/https://eldritchtrender.tumblr.com/post/185489664748/eldrigender-a-gender-or-lack-thereof-which-is archive
- [https://web.archive.org/web/https://en.wikipedia.org/wiki/Elder_Sign Elder Sign ]