The Pet Monster is a supporting character (usually an NPC but possibly a token evil team-mate PC) who is unquestionably evil, but still well disposed towards one of the "good guys". The monster may serve as a sort of inverse morality pet for the protagonists, or as the one who takes care of the jobs that the PCs are too "good" to do.
Interesting examples might include an evil orphan who is actually quite attached to their adoptive family and will go to horrific lengths to protect them, a evil fairy Godmother who takes her Godmotherly duties seriously, an undead ancestor with an interest in furthering the destiny of his descendants or some kind of monster (say, a dragon) that the protagonists raised in the hope of bringing it up as a force for good - unsucessfully for the most part, but enough that it retains affection (or a sense of debt to be repaid). A creepy, stalkerish villain with a crush on one of the PCs might also be interesting - perhaps a vampire with an interest in a female protagonist?
A more mundane - and entirely historical - example might be a condemned murderer, whose execution is indefinitely suspended as long as they are prepared to serve as the community's executioner. Although the contract need not be that leonine - plenty of sadists and other thoroughly unpleasant people have been employed to do what they enjoy by governments of all kinds through the ages, whether killing for entertainment, carrying out political assasinations or as torturers. Degrees of freedom may vary from case to case, but this may not matter much to anyone involved. Obviously, in these cases, the pet monster is not working for "the good guys" … but may be working alongside them.
Game and Story Use
- Can make for some interesting moral boundary play as the PCs debate letting their supernatural ally deal with all sorts of problems which would be better not resolved with violence.
- The monster may also lack a sense of proportion - argue with a colleague over parking spaces at work, wake up the next morning to find that your creepy vampire with a crush has left their head on your doorstep. Nice.
- Even more fun if the monster is not necessarily evil but more childlike and powerful, lacking much in the way of moral sense or empathy and recognising only its attachment to the PC.
- Also good for playing "good cop, bad cop" possibly with cops.
- Speaking of which, there is significant plot potential in trying to avoid the consequences if your PCs is arrested - how do they prevent their pet monster from getting all Terminator I in an effort to rescue them.
- The truly domesticated pet monster may not show their true colours until someone triggers their Roaring Rampage of Revenge - at which point the trail of destruction that they generate should be expected to be impressively horrific.
- This can be played for aesops if someone kills off a character that was in the process of reforming a former villain. Even more so if it's the PCs who hunt down a villain who is trying out for the role of the atoner and, for whatever reason, remove his incentives to go straight.
- Very useful if it's a PCs backstory villain - they are then faced with a conflict between resolving their backstory (which is important in some systems and/or can related to various advantages or disadvantages purchased at character creation) and causing all kinds of unecessay devastation or leaving their backstory unresolved but, quite possibly, learning an important lesson about redemption. GMs should be clear about which choice is correct or set things up so that the player doesn't lose out from a plot-forced decision.
- Some players may actually revel in this role … and in making other players run about preventing them from "triggering" … or cleaning up afterwards. May disrupt play or enhance it, depending on your group.
- The mundane version can make a hilarious colleague for PCs working for a less than scrupulous patron…