Warhammer works great!
How many leucrottas seem appropriate for the summon ability? I'd peg a single one worthy of summon monster IV or V, and this is the equivalent of summon monster VII.
Organization: Solitary, family (1-2 plus 2-4 mummies), pack (1-2 plus x-x leucrotta plus 4-8 mummies), or divine council (3d4 composite mummies of various types)