what is this?????
It is
Bishop'ssssssssssssssssssssssssssssssss♝!
It's positions with a lot of Bishops on one side (and one of opposite color on the other side) that apparently have a forced checkmate as the solution for the side with less material. Unfortunately I messed it up by posting a position that added Knights, but I think my good friend the OP didn't mind.
Can't believe a mate in 10 wouldn't be within the calculations horizon, literally the bishop move to a6 trapping the king is obvious, and then the mating pattern that follows is just as obvious.