Jackalweres keep summoning Jackals
Jackalweres don't get tired from summoning
I was playing a barbarian and ran into a Jackalwere in a random dungeon and fell asleep. After that the Jackalwere wandered off and summoned the entire level full of Jackals. Literally one Jackal for every free tile.
I leveled up from 8 to 16 killing them until I managed to find and kill the Jackalwere. It was still summoning Jackals until I finally killed it.