Day 1

Bellow barely make it down without falling and wait for Elrond or Anguis to help him out.
Elrond, Anguis anyone helping Bellow with a rope ? That will require no checks, just your free will to help.

You are squeezing at the cave entrance and see corridor going further, the corridor turns left - to the north.

The cave 5 ft high at the entrance and coiling goes up, floor goes horizontally 20 feets, but then start going up as well and almost meet the ceiling so it is hard to see how it ends. You will need to go up to see. There are sort of ladders that will make it easy to go up.

You see that the steps up are man-made and they look "used", it is quiet otherwise.

Since you did not explain what exactly are you doing I want you to roll wisdom check (d20+your wisdom modifier) to see how exactly is he "scanning".

Elrond see the dust is distributed equally and he see no evidence of crawling creatures on the walls or ceiling, so he conclude that the creatures that could be here are either floating, Incorporeal or just a creature that does not need to move/feed, such as zombies.
The steps you see in front of you and the ceilings right above them seems man made, most probably ceilings were too low here and it was made higher, but this is the only feature that seems unnatural in the cave.

there are more. They take you 10 feet upwards and you see that cave other end goes back into tomb. You see a room with altar and two chests on the altar. Chests are exactly same as you seen in the cavern.

I assume Elrond do understand that this way he will not find traps that trigger when more than 10 pounds of wight are applied.
And no your mage hand technique do not reveal anything.

Nevertheless, you have made dust from the floor go up in the air. You sneeze, but see floor similar to the one in the big hall. You realise however that the floor behind altar seems half inch lower - apparently monks have been spending a lot of time next to the altar.

Anguis feel relief as divine senses detect no Celestial, fiend, or Undead within sight.
Note for everyone as you look around you could see decayed bookshelves in the room to the left. You realise that the chests are the only things that looks fresh and not covered with dust here.

no threats. By pick up you mean put it into the bag of holdings? Both of them? Or do you open them on the altar? They are each rather heavy. You can carry one at a time.