The 5e SRD has recently been released under Creative Commons (https://www.dndbeyond.com/attachments/39j2li89/SRD5.1-CCBY4.0License.pdf). 

That opens up many new possibilities of use for the SRD.

It even allows you to use some names that were not covered by the OGL, like "Beholder" and "Mind Flayer".

Make anything you want, as long as it follows both the rules below:

1. Be sure to use the Creative Commons SRD and follow the legal instructions found on its front page:

"The System Reference Document 5.1 is provided to you free of charge under the terms of the Creative Commons Attribution 4.0 International License (“CC-BY-4.0”). You are free to use this content in any manner permitted by that license as long as you include the following attribution statement in your own work:

This work includes material taken from the System Reference Document 5.1 (“SRD 5.1”) by Wizards of the Coast LLC and available at https://dnd.wizards.com/resources/systems-reference-document. The SRD 5.1 is licensed under the Creative Commons Attribution 4.0 International License available at https://creativecommons.org/licenses/by/4.0/legalcode.

Please do not include any other attribution regarding Wizards other than that provided above. You may, however, include a statement on your work that it is “compatible with fifth edition” or “5E compatible.” 

Section 5 of CC-BY-4.0 includes a Disclaimer of Warranties and Limitation of Liability that limits our liability to you."

2. Submissions that promote racism, xenophobia, ableism, transphobia, homophobia, or any other form of bigotry or hatred will be removed.