I'm interested in creating a trading card game based on something that exists already. Lets say for example the existing game is Dota, Defense of the Ancients, which was a custom game created within Warcraft 3...the website is DotA-Allstars.com - Welcome. At the bottom of their website it says the website is Copyrighted. How would I go about finding out if I can go ahead and create a card game based on something like this? I found these two websites to look up Copyrights and Trademarks...in my case which is more important to me, or is it both? For Trademarks... http://tess2.uspto.gov/bin/gate.exe?...ate=p01oug.1.1 For Copyrights... http://catalog.loc.gov/cgi-bin/Pwebr...cal&PAGE=First When I look up "dota-allstars" on the Copyright site I find nothing, when I search on the trademark site it says the following. What kind of research would I have to go to give myself the green light to go ahead and create a game and possibly sell it at a future date?