When striking a killing blow on a diggle farmer with melee combat on floor 2, the game will crash, however they are killable without a crash using ranged combat. I've been experiencing this since the wizardlands patch. Another glitch is Diggle Adventuring Team Memebers gaining like 50+ stacks of the Radial Diggle Buff, which seem to cause them to do something around 20 damage a hit.
Both diggles in question are from Fax's Debacle of Diggles mod. (Side note: IRHYP is also running the Mimics mod, perchance?) (Side side note: FAAAAAAAAAAAX!) I'm not sure about the Farmer (there's not anything particularly quirky about its xml), but Radial Diggle Buff should only have a 10-turn duration, so ... run like you stole something (from Brax), then get your murder on once it calms down?
Oh... I didn't know they weren't base game, you see I thought that the mod just increased their spawn rate, not added more. Also @Arron, my avatar is of Eureka, google Eureka 7.