Mother of Giants
The Mother of Giants is a collection of adjacent Turing machines, some of which are Cryptids in the 5-state Beeping Busy Beaver problem that probviously quasihalt. They must all be proven to halt or not if we want to solve BBB(5).
The TMs are all the "children" of 1RB1LE_0LC0LB_0LD1LC_1RD1RA_---0LA where children means all the TMs created by filling in the undefined E0 transition.
See https://www.sligocki.com/2022/04/03/mother-of-giants.html for details.