Their leader, Falco Spara gives you a shield counter, and then lets you cast creatures from the top of your library by using counters
If an effect allows you to put a card with particular characteristics onto the battlefield without instructing you to play or cast it, you consider only the characteristics of a modal double-faced card's front face to see if that card qualifies
Firstly, it lets you cast birds or lands off the top of your library
It seems a natural question to consider whether Desecration Demon could go in our Demons deck, but unfortunately it doesn't seem very likely that this is better in the foreseeable future than Archfiend of the Dross, and there's a limit to how many creatures like this (somewhat expensive and vulnerable to the same play patterns) that you can play at once so it's also unlikely we'd play both at once
Whether its a combo, tribal payoffs, or other general synergies, having a crucial game piece always available in the command zone is essential in the best decks