After opening the gate and lighting the braziers, as shown in part 1, go after the MAX AMMO UPGRADE hovering below.

In the single-player game, stand on the upper left side of the ledge with the single, round column and grapple the golden ring across the gap. Move around the left side of the column and then step toward the lower right edge...

...so the grapple cable wraps around the column, as shown above. Now step off the edge and rappel down the wall, taking care to stand between the 2 sets of ice vents mounted on the wall.

Once you're hanging below the ice vents, wall-run to the left a little to snag the upgrade. Then climb back up the way you came and return through the gate near the pressure pad to the room below.

NOTE: I experienced a bug in the single-player game in which this ammo upgrade did not appear, so I had to Photoshop the icon into the above screenshot. I hope you won't have the same problem.

In the 2-player co-op game, there is no golden ring. Instead there's a second pressure pad. Have Isis or Horus stand on it to deactivate the ice vents on the ledge with the round column. Then Lara can jump across and light brazier #42.

Lara can then grapple the other character while s/he remains on the pad. Once the grapple is secure, Lara should move around the left side of the column so the grapple cable wraps around it (as indicated by the white line in the screenshot above). She can then rappel down the wall to get the upgrade (red arrow).

Multiplayer co-op works the same. One player stands on the pad while another grapples him or her and rappels down to the upgrade.

NOTE: I will add better screenshots of the co-op versions as soon as I can.

[Part 1 | Return to the Tomb of Hoarfrost Walkthrough]