Steven Jelly said: Brian C. said: IANAL, but I have released several 5e adventures on the Roll20 marketplace and elsewhere. The short answer is that you must get permission to use everything that you do not create from scratch. This includes game mechanics, art, maps, music, and plot. For the 5e game mechanics, Wizards of the Coast (WotC) has released the System Reference Document (SRD) under the Open Gaming License (OGL). You can get a copy here . It defines the game mechanics, monsters, spells, etc. that you can reference in the adventure along. You may not use something that is in a WotC product that is not in the SRD. So you could use a lich as a bad guy, but the demilich is not allowed because it is only in the Monster Manual. The OGL also allows the creator of a product sold with that license to define parts that may not be used because they fall under "Product Identity". The SRD restricts things like proper names, WotC campaign settings, and certain iconic monsters. For art, maps, music, and the like, you need to get a license from the seller, who often also the creator. Some content is release with a license that defines how you may use it, and others reference various versions of the Creative Commons license. Some art creators on the Roll20 marketplace are willing to grant a license to adventure creators. I hope that helps. Let me know if you have any other questions. Thank you Brian for the very informed response! And thank you as well Triva for the additional info. I plan on creating the art and maps myself so there is no worry about that. I was just curious about the licensing regarding what rules, monsters, and races are available for me to use when writing and creating the adventure. And just to clarify, everything in the SRD is open to use in a 5E Adventure? Besides certain WotC products (For example, the Forgotten Realms Setting or your example being the Lich vs Demilich) And thanks for the SRD link, it’s exactly what I was looking for. I’m gonna be reading through it carefully this evening. You're welcome. My understanding is that the first page of the SRD (the "Legal Information" page) tells you what you can and cannot use. It says you can use everything in the SRD (after the "Legal Information" page) except for any items listed as "Product Identity" in the fourth paragraph of the "Legal Information" page. If something is in a WotC book but is not in the SRD, don't use it. If something falls under "Product Identity", don't use it. Also, don't forget to replicate the OGL in your product exactly from the "OPEN GAMING LICENSE Version 1.0a" to the "END OF LICENSE". In section 15, you must include all OGL products from which you have used content in your product.