Locally toroidal polytopes of rank 6 and sporadic groups

We augment the list of finite universal locally toroidal regular polytopes of type {3,3,4,3,3} due to P. McMullen and E. Schulte, adding as well as removing entries. This disproves a related long-standing conjecture. Our new universal polytope is related to a well-known Y-shaped presentation for the sporadic simple group Fi22, and admits S4×O8+(2):S3 as the automorphism group. We also discuss further extensions of its quotients in the context of Y-shaped presentations. As well, we note that two known examples of finite universal polytopes of type {3,3,4,3,3} are related to Y-shaped presentations of orthogonal groups over F2. Mixing construction is used in a number of places to describe covers and 2-covers.