Once you've opened the bars, as shown in part 1, return to where you first entered the Sunken Chapel area from the Shrine of Osiris. Climb onto the ledge above the bricked-over wall.

Now that the bars are open, you can reach the MAX HEALTH UPGRADE and time bomb.

The time bomb will not fit through the doorway where the bars were, and flame jets prevent you from pushing the bomb off the right side of the ledge. Raise the Staff of Osiris to slow the countdown on the time bomb as you push it closer to the flame vent.

Then plant a remote bomb behind the time bomb...

...and detonate the remote bomb to blast the time bomb over the flame vents and off the edge. You can't jump over the flames without dying, so instead drop down on the left...

...and head downstairs to the courtyard where the time bomb landed.

Still keeping the Staff raised, roll (or blast) the time bomb up the stairs...

...and push it against the crumbling wall near the pillar with Osiris's glyphs.

Once the bomb is in place, lower the Staff and let the bomb explode...

...destroying the wall and revealing a MAX AMMO UPGRADE.

[Part 1 | Return to the Sunken Chapel of Sobek Walkthrough]