How to open gate in the same room as 2nd Dragon? (Level 5)

[Skirmisher]

Need info on opening the gate to the one square cell located in the same room as the 2nd Dragon Gaze. The 2nd Dragon Gaze is the one gazing south. In the same room, west side is a gate blocking entrance to a one square cell where loot can be found. There is a button on the back wall of the cell.

[Ugm]

hint:

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it's a timed event

and

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it has nothing to do with the dragons actually