I’ve always loved the humble otyugh, enough that I wanted to create some more lore for it. I wanted to have a lifecycle for this oddity. As an aberration, I figured it wasn’t the way that humans find “normal”, but likely something a little more peculiar.
Here’s the Otyugh Stat Block from the Basic Rules:
Otyugh Fragmenter Lore
The otyugh fragmenter is nearly indistinguishable from it’s non-fragmenting cousins. It is slightly larger, more easily cut, and more aggressive. Adventurers familiar with them also refer to them as bladeseeker otyughs. They tend to preferentially engage with items that can cut them, as getting cut is a necessary part of their reproduction.
When cut, the piece that falls off grows into and otyugh whelp. This growth can take as little as 24 hours in food-rich environment such as a sewer, garbage dump or swap. The whelps must attain full size before they are able to fragment again. Even so ,The whelps are a significant problem in their own right. Lacking the size to grapple, they settle for tripping their foes.
Running the Monster
I recommend narrating the chunks falling off of this monster as descriptively as possible without tipping off players as to what is coming next. Also, plan to have a way to keep the players around until the whelps have had time to mature and wreak havoc. Happy townsfolk reward them with a night of drink and song for killing the monster. Then they awaken late the next afternoon to the sounds of a town overrun by fun-sized otyughs
The fragmenter can take more damage than the normal otyugh. That said, it’s vulnerability to slashing damage will make it significantly easier to kill. The fragmenter should focus it’s attacks on PCs that deal slashing damage, as this will give it the best chance of reproducing. Have fun!