[7] SyFy Wire in 2018 called it one of "The 9 Scariest, Most Unforgettable Monsters From Dungeons & Dragons", saying that "Eaten by an ooze that can then use your memory and form to trick and lure others in?

[9][10] In May 2022, D&D Beyond stated that users will retain access to previously purchased copies of Volo's Guide to Monsters and Mordenkainen's Tome of Foes.

[11] Christian Hoffer, for ComicBook.com in May 2022, commented that "one major concern about the delisting is access to the chapters of lores contained in Volo's Guide to Monsters and Mordenkainen's Tome of Foes.

The score was lowered due to the lack of a PDF version that didn't rely on a third-party app, and for reusing verbatim much material from previous editions.

[...] Asmodeus, the lead devil of the cosmology, is delightfully Satanic, and even reading through the book I was trying to figure out how to fit him into the campaign that I am currently running without disrupting the flow and feeling of the world that I am working in.

They are books that are grounded in the dusty roads and dirty swords of fantasy tabletop campaigns, and they slot easily into the workflow that I have to make those kinds of adventures feel good.

[16] Rob Hudak, for SLUG Magazine, wrote that "Tome of Foes has little mechanical application for most players outside of the additional playable races, save for probably the most important facet in all role-playing games—inspiration.[...]

Tome of Foes may have the pages you need to conjure richly imagined facets for both playable characters and narrative threads alike, and I think it’s in that latter category where this book offers the greatest value.

Referring to my review of Xanathar's Guide earlier this year, I see that I gave it a 9.5, docking it only because I thought it wasted space on a mostly useless appendix.