M3_TRAITOR monster flag denotes monsters that have a chance of spontaneously rebelling against the player when tame and becoming hostile; dNetHack uses
MT_TRAITOR for the same purpose. Monsters that have turned on you will additionally have the text "traitor" added when examined with a stethoscope or wand of probing.
The check for betrayal occurs whenever you abuse the pet, as well as with a 1 in 850 chance on every move. The betrayal check will always fail if the pet is a spell being, is further than 3 squares away, is mindless, or if you have more hit points than the pet. If those checks pass, then there is a chance that the pet will turn traitor. Thus, increasing the pet's tameness and not abusing them will decrease the chance of rebellion, but the only "certain" way to eliminate chance of it occurring is to raise your HP.
- <foo> turns on you!
- A tame monster with the "traitor" flag has spontaneously become hostile.
- You feel uneasy about <foo>.
- As above, but you were unable to see the former pet at that time.