Relics and Documents | Path of the Deathless Rise of the Tomb Raider Guide
Relic 1 (Mysterious statuette)

Right after you fight two deathless, under archers' fire - defeating them opens up path ahead. The relic is by the skeleton, next to the wall to the right of the gate.
Document 1

Right after you enter from the Planetarium, on the rock to the left.
Document 2

A bit past camp Guards' chamber when you have to walk under lumps of ice hanging above, Lara "hugs" the wall. Right after you get to the other side, find a small recess to the right - there is a corpse there and the document is on the corpse.
Document 3

Right after the fight with the two Deathless, under archers' fire - defeating them opens up the path ahead. The document is right past the gate.
Document 4

Behind the same gate as the previous document - after you cross the gate, approach the edge on the left of the gate.