Fluids, metamorphism and metasomatism including serpentinization and magmatism can weaken the lithosphere and lead to mechanical and chemical processes that affect the strength and slip behavior of fault zones. However, the competing mechanisms that control strain localization and exhumation rates and the nature of fluids during these processes are still poorly understood. In the first part of the talk, I will show the importance of in-situ apatite petrochronology from three subduction complexes in the Hellenic subduction zone. Apatite preserves subduction processes including metamorphism, metasomatism, and underplating due to its ability to deform, recrystallize under pressure/temperatures conditions associated with the base of the seismogenic zone. We show that during exhumation apatite records aqueous fluids that were derived from metamorphic dehydration reactions within the underlying slab and migrated along lithologic contacts, thus revealing the interplay between deformation and fluids that likely contributed to slow slip and tremor along the plate interface.