Valve has just trademarked a new title in the works. The trademark was filed under the name "Dota Underlords" and this is the secret working title (or perhaps even the real one) of a project that is currently under development at Valve.
Dota 2 is one of the most popular games available on Steam. The game also has one of the biggest esports events in the history of gaming. Dota 2 has also allowed for custom lobbies and custom games to be built in the "Arcade" section of the game, much like how the original Dota was a custom map creation in Blizzard's Warcraft 3.
One of the most popular custom games to come out of this Arcade mode is "Auto Chess". Auto Chess is a simple game where you get custom pieces to fight for you and players can choose to upgrade those pieces too. It beats the fast-paced lengthy matchups in the regular game mode so it has gained a lot of traction among players.
Auto Chess is also getting a mobile port, developed by the same group of developers. Valve has only released one other Dota spinoff, which was the trading card game Artifact. Artifact has not been doing well at all, consistently dropping in the number of players and not having a great strategy.
Could "Dota Underlords" be a separate, monetized version of Auto Chess? It wouldn't be new anyway. Popular Battle Royale PUBG started off as a mod in the military simulator Arma 3 and then became an independent game on its own. The number of players in Auto Chess also gave rise to a huge spike in the number of people playing Dota 2, so Valve is definitely interested.
Valve is developing games for its new VR headset, the Index. They are also working on new VR titles for Steam and to support the Index. For now, we'll probably have to wait and find out what "Dota Underlords" really is.