Trying up before down

You took a few moments gathering yourself, while studying the various pockmarked holes across the curving cave walls. Veterans to this dungeon always urged caution and planning over haste- the Furrow opened gates to worlds never before seen, threats never considered. And it never seemed to deposit its travelers into benign, peaceful locales. So despite the peaceful appearance, you were sure there was someone or something that called this cave system its home.

[Rolled a 17+2 = 19 on Perception]

Though as the minutes dragged on, and no nasty creepers offered a census of their local population, you concluded that you were alone for now. There also were no obvious signs of traversal along these walls, at least none by beings intelligent enough to install pitons or other vertical movement aids.

Remembering, you awkwardly scrabbled at your travelling pack's loops, like trying to scratch a difficult to reach itch. You pulled out a small ice axe, testing its weight and anxiously tugging at the head to ensure it was well built. Normally useless in rocky terrain like this, it was a prime example of the investment you were making in this trip; an adamantine alloy pick allowed it to drive deep into stone without dulling. You secured a few more ties on your pack, double checking it was latched shut, and began your ascent.

It made more sense to climb first, because if the bottom was a dead end you'd be burning through calories at an exorbitant rate climbing back. So with careful precision and healthy fear, you took it one step at a time. The pick drove into the rock with a satisfying TNCHK, allowing you to secure your hold a little higher with each driving strike. The vibration of the impact made your arm sing with an unfamiliar soreness, more bone than muscle, but it made a treacherous ascent far less daunting.

After several minutes, you found yourself at level with the largest of the waterfall openings, only a lateral climb to go before being able to take a well earned sit. You took a moment to peer inside. The dim light of the fog that rolled above you much closer now, but its ambient light did little to pierce the deeper reaches of the tunnel. The water surged over the edge, it looked misleadingly slow due to the sheer size of it. You knew it would be impossible to outswim if you happened to fall into it. Luckily, the water cut walls gently sloped into its bank, giving a clear path alongside the channel so long as you watched your step.

It took a little further effort to traverse to its opening, the sound of the fall vibrating deep in your chest through your firmly planted feet and arms. The rush of humid, cool air chilled you, as you took extra care to come off of the wall and onto the slanted floor. It was not a regular curve, eras of differing water volumes cut different silhouettes of rivers from different times. It gave more of a natural stairway, sloping down and straightening in an organic manner. You sat, butt on one of these shelves, feet on a lower one. A small pleased hum escaped you, pleasantly surprised at the comfort.

Your rest, however, was interrupted as you heard something echo from somewhere beneath, muffled by the water but distinctly separate from the natural ambience of the cave. Focusing as your heartbeat quickened, you dared not move as you tried to figure out what you were hearing. There was a somewhat regular clacking noise, like stone on stone, and then some kind of animalistic warbling that cut through the rush of water. You internally debated on peering out over the lip to see what just arrived...