Battle Pass owners can give friends three keys for Dota Underlords
Valve allowed all Battle Pass owners to donate three keys for Dota Underlords to friends or acquaintances who do not have a Battle Pass. So developers want to increase the audience before the start of open testing.
You can get the keys on the game page in the Dota 2 client or ask any friend who already has a Battle Pass. You can activate the code in the Steam library.