This page explains how to find the Ishto Soh shrine and solve the "Bravery's Grasp" puzzle.
How to Find the Shrine
You might find it helpful to activate Lake Tower before you look for this shrine.
Go to Ka'o Makagh Shrine, then go west to reach Harfin Valley. Go across the Menoat River, then go southwest through Pappeto Grove to reach Darybon Plains. Go west from there through Nautelle Wetlands. Go part way north through Oseira Plains, but look west for a place where you can go up the slope. The shrine is on a plateau northwest of the Nautelle Wetlands.
How to Solve the Shrine
Look down below to see a laser shooting at a wall. In an alcove beyond the laser, there is a treasure chest. Float down to it from the ledge where you entered the shrine. It contains topaz.
Then pick up the thing that is shooting the laser. Set it down beyond the moving platform so that it is shooting at the crystal switch, with the moving platform blocking the laser each time it goes past. This will make the columns in this room rise and fall.
Go up the ramp to the area where you entered the shrine. Stand on the small ledge that sticks out, and when some of the columns go farther down, float to one of them.
When the columns change, stand on the one nearest to the treasure chest. When it goes up, go to the treasure chest and open it to get an Ancient Core.
Then go to the columns next to the metal wall. Whenever the columns change, go to the next set of columns until you reach Ishto Soh.