Geophysical data demonstrate elevated seismic activity in subduction zones. Here dehydration and fluid pressure cycling as a function of increasing compaction and metamorphic grade are closely linked to deformation over a multitude of spatial and time scales. The highly anisotropic and initially fluid saturated marine sediments and altered oceanic crust dehydrate, while being incorporated into the accretionary wedge and subducted under the upper plate. Under high tectonic stresses, fluid overpressure eventually results in mechanical instabilities, promoting either hydrofracturing or ductile failure giving way for fluids to circulate. Collection of these fluids at the micron-scale and propagation along pathways up to the deca-kilometre scale are probably in charge for phenomena such as episodic tremor and slow slip. Increasing evidence from geophysical and seismic studies suggest that accumulation of slow slip events and fluids may even trigger devastating high-energy megathrust earthquakes. Quantitative understanding about (i) the release of fluids from their host rocks, (ii) the effect of localisation of both fluid flow and deformation and (iii) their effect on seismic activity are therefore crucial to understand the complex feedback processes. This system can only be fully understood by a close collaboration between experts from structural geology, metamorphic petrology and geophysics. In this interdisciplinary session, we therefore invite contributions from natural, experimental- and numerical modelling-based studies focussing on both exhumed (paleo) and active subduction zones.