Some of the monsters through the history of the game lend themselves to inventing reasons for them to exist. This is an attempt to show how 3 monsters fit together even if going by the rules wouldn't quite make sense. F it, it's magic!
Our subject today is the Roper.
In caverns deep there are horrors aplenty just waiting to make a meal of your frail adventurer. It could be things like the Mimic and it's cousins the trapper, lurker, etc. In this case we're looking at the Roper and what it might look like at various stages of life.
I posit that what we know of as the roper is the adult form of a very long lived monster:
The monster is rare and that is a good thing since a monster of such power and intelligence could control or wipe out whole underground kingdoms should a group of them be so inclined. Thankfully then they are chaotic.
But what do they look like and behave like when they are younger and not so powerful?
Perhaps this is their juvenile form:
Moving on to what I believe to be the larval form of the dreaded roper:
Once down below they are so slow moving that surviving prey can often slaughter them before the beasts can climb back up to safety. This might account for the large number encountered at any time. Their hardened shells help buy time for some of them to reach safety and grow into the juvenile form.
Of course this could all be a flight of fancy and these could well and truely be unrelated monstrosities inhabiting similar niches in our magic rich world.
Yours with curiosity and imagination,
Prinportia the Sage, of Loreltarma