By its very nature, this is the kind of mechanic that doesn’t come up very often, but here’s a real example of a time when it happened twice in quick succession and worked really well.
Stomp, Vega, and the Sheep-field
So, uh, this one is going to take a bit of explaining. This was a weird, post apocalyptic game that I’ve mentioned before when talking examples because it’s probably the game I’m most proud of.
Winter was approaching (the wolf-god of ice and snow) so unseasonable cold was coming to Steel City. Vega was the boss of a settlement, and she needed warm clothes and blankets for her people. She tracked down a factory outside of the city that produced wool from a sheep-field (an entire field that was a “sheep”, multiple acres of carnivorous wool) but she couldn’t keep trekking to and from the factory with these items, so she bargained for a section of the field to take back home.
Stomp was Vega’s chief enforcer, and had been convinced (coerced) into being the one to cut this section out and bundle it into a truck. He dives into the wool and starts hacking away, taking severe damage but surviving. A blizzard is rolling in at this point though, so they have to hurry back before they get snowed in. The cold becomes biting, almost literally, and Stomp takes a small about of lethal damage and succumbs to his existing wounds. I ask the player how he wants to come back, and he declines because his death is dramatic and appropriate. Always offer your players the choice.
Vega is distraught that she caused her chief enforcer to die, and furious at the sheep-thing, but her settlement comes first. She offloads it into the pen they’d built as the snow piles up, but rather than moving the sheep-thing expands to fill the new space. After severing the connection, the two halves both live. Vega needs her truck back, and senses an opportunity for some revenge, so she pulls the machete from Stomp’s cold body and goes on the attack. The sheep is dangerous, and she’s on her own, so despite her righteous fury Vega is brought down.
The following day, some other members of the party go out searching and find the truck. They pull the now-dead wool out and find Vega in the back, barely alive. A sheep skull is pinned to the wall with the machete, with Vega’s blood on its teeth.
Yet another day later, Vega has mostly recovered. She heads out to the truck, pulls the machete from the wall and dons the sheep skull as a mask. Rather than a shrewd and cunning leader, she is now a bloodthirsty berserker.
Campfire Story
That took a lot more text to properly describe than I first thought, but I hope it gets the point across. The key is to make it fit the narrative and the player’s desires. Let me know if you have any questions about my decisions there. I have maybe one more real example, and some thoughts about how I’d handle it in my currently ongoing game.