This mission is located past the frozen bridge past the ice lake (close to a glacier troop and its ice driller). Cross the bridge to find the flut flut on a trans-pad. Mount it and walk over the nearby precursor metal button to activate a number of floating platforms as well as a ticking timer. The platforms have to be crossed quickly enough before the timer runs out, periodically you'll reach a safe area with another button.
The jumps get progressively longer and harder with more moving platforms, there's three sections total. At the end you'll end up at another trans-pad and a power cell on top of a button next to a lurker mechanism. Grab the cell to simultaneously open the gate to the lurker fort.