It looks like another Dota spinoff might be in the works again at Valve. A trademark filed May 6 by the Valve Corporation for "DOTA UNDERLORDS" caught some eyes this morning, possibly indicating a new spinoff or other games in the Dota universe.
No further info is out at this time, as this is likely a portent of some announcement in the future, probably at a venue like this year's Dota 2 International. Considering where Valve currently stands, there are a few likely options for Underlords.
The first is that it's somehow related to Artifact, Valve's Dota-centric card game that has fallen on hard times as of late. Major departures from the Artifact team and a recent statement indicating a need to course-correct have beset the tri-lane highway, so Underlords being a refresh (a la Dota's Reborn update) is one possibility. However, Valve made clear the separation in brands by not affixing the Dota prefix to Artifact, and it would be strange to double-back on that now.
A more likely answer is that this is Valve's answer to Dota Auto Chess, a mod for Dota 2 within the Dota 2 client that has taken off in popularity. It's best to simply describe Auto Chess as competitive tower defense, but it has a depth that's attracted streamers and players alike. With the team behind the mod, Drodo Studio, bringing their game to mobile platforms, sans Dota references, it's very likely that Valve is looking to launch a competitor or standalone client. And what better place to announce it, than to a stadium full of Dota fans who have likely already been playing Auto Chess for some time?
An outside shot is a battle royale or other type of competitive spin-off. On name alone, this could be a callback to the Underhollow, a battle royale mode Valve included in last year's battle pass for the International. That seems unlikely, given a trademark would rather indicate something standalone than a big patch update or limited-time mode, but it's not outside the realm of possibility.
Time will tell what Underlords ultimately is, though we're likely to not learn anything until the top Dota 2 teams in the world clash at this year's International in Shanghai, China. We've reached out to Valve for some clarification, and will update if we receive a response.