What is the Red Triangle next to the Ulti Diamond at the top of the UI

So on the hero pictures at the top, there's a red triangle with the point placed down. It's on the outside bottom of the top. Also the same triangle appears on the large animaged profile picture when a hero is selected..

I stopped watching for 6 months, and I haven't been able to figure out what it's for.

1 Answer

That badge means the player has reached level 1 to 5 of that hero's progression system, part of Dota Plus subscription.