You can't do anything with the glowing sphere yet, so leave it for now. Grapple the golden ring ahead on the right and climb onto the ledge above.
Move around to the left and stand on the pressure pad to temporarily retract the spears sticking out of the wall above the spike pit.
Quickly jump across the gap before the spears pop out again. (Standing on the second pad retracts the spears again but they only stay retracted as long as there is weight on one of the pads.) Use the Staff of Osiris to destroy the Mark of Set in the alcove. Doing so opens the gate below.
Climb down on the left, get the illuminated sphere, and roll it up the stairs onto the tile with Osiris's glyphs.
Raise the staff to extend a column, lifting Lara and the sphere to ledge above, so you can then roll the sphere onto the pressure pad.
Plant a remote bomb behind the sphere. Jump across the spikes and stand on the other pressure pad.
This will keep the wall of spears retracted as you detonate the bomb to launch the sphere across the gap.
Catch the ball and roll it away from the edge but don't put it in the cage yet. First place another remote bomb below and to the right of the round pedestal near the raised gas vent. (There's a scorch mark on the floor indicating where to place the bomb.) Then roll the ball onto the pedestal.
Detonate the bomb to launch the ball upward. The fire inside the ball should then light the gas...
...opening the gate on the left so you can get the MAX AMMO UPGRADE.
Finally, roll the sphere into the cage to open the exit.
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