I just loaded a copy of Wildemount. It has a Beholder in the module, with artwork. In general, if a creature is unique to a book, it will be in that book's compendium. If the creature as provided in the book is merely a reference to another source (Ex. "Bob is a beholder ." with no printed statblock) the module will only contain an in-game copy, with no Compendium content. This mirrors the experience of buying the Wildemount book. Buying that physical book would not automatically give you the Monster Manual copy. I.e. by buying the Wildemount book, you get what is in the Wildemount book. By way of courtesy and with the permission of WotC, you are also given a fully working copy in the game. Roll20 also does this for specific rules and systems that may be referenced by the module, but not in its text, and not in the SRD—you get a handout with the referenced material. I.e. compendium content is only provided for things actually in the print version You could move such a monster to a different game in one of two ways: As a Plus user, you can use the Character Vault. Export it from your Wildemount game and Import it into another. Pro users also have the Transmogrifier, which allows you to freely move monsters, maps and more from one game to another, provided you are the creator of both games. Finally, if you have the Beholder from a purchase of the Monster Manual, you can drag that beholder into any game that uses the 5e Compendium and for which you have set up the sharing to allow it (usually the default is to share everything). If for any reason, there is already a Beholder in the game, you will only create a new instance of the existing Beholder. For example, if all Wildemount Beholders had an Irresistible Dance ray, and you dragged in a Monster Manual compendium beholder to that Wildemount game, you would still only have the modified beholder in that game. If you need both, just rename the existing copy in the game and the Compendium drag will pull in a true MM version.
