After taming the manta rays, we didn't waste any time.
Only we didn't keep heading forward in the same direction.
Instead, we turned around and started moving in the opposite direction, meaning that we were going back to the same place as before.
When we came back, all I did was leave the manta rays with the gnome who looked very uncomfortable at being left alone with the manta rays. Only I didn't care what the gnome thought or how he felt.
The only thing that mattered was gathering our forces in this dungeon and getting as much information as we could.
So other than leaving behind the manta rays, I also dropped off another load of monster cores for the gnome to keep producing sets of living armour with.
With the Scavenger Rabbit's ability, it was easy for me to get all of these monster cores. At a certain point, they were just taking up space in my Storage Ring.