Collectible Card Game Headquarters

Steam workshop is a place where you can submit mods, so all players that have the game can download them and play online. It's possible for dotp13 or maybe a future dotp game? Online is the fun in this game.

That is more of a question for WotC rather than us. From what I understand a game has to have been authorized for Steam Workshop (in other words the game creator has to pay to allow their game to use it). Also that would probably require that WotC unlock the game so that mods can be plugged in properly (so custom decks can actually be saved properly, sync testing so that you don't try to play against people who have cards you don't and vice-versa, etc...).

I think one of the reasons they probably won't do this is because of Magic the Gathering Online.