Get 2 water assists and maybe earth with terra. First water assist casts freeze on top 2 mummies, then second casts freeze on bottom 2 mummies. Earth uses terra on eva. Then you kill mummies when there will be only water ones. When there are 4 water mummies, kill Eva. Then just kill spawning mummies one by one, if there's only one debuffing mummy it shouldn't be big problem.