Adding pack rothes that have beefy HP but offer little to no damage or AC at all.
It would be a nice addition for stone runs on my duergar, and fits the duergar caravan vibe all too well.
Obtained maybe from a duergar rancher in the trade post or something like that. Can be an item you use and it has infinite uses or once per day.
it'd need a surface counterpart for surface players too obviously. it would work the same as the ooze tubes once did, but their use is in the back of the party. items would be lost on reset but works as a good buffer to carry items in a short term period like ores, stinger barbs, stone, etc. maybe wizards can get the floating disk spell as well to similar effect.
animal empathy after getting a rancher to spawn them could also be an option, requiring players to have some degree of animal empathy (10-15~) ??