This ocean-bottom seismometer deployment is part of the LoCHnESs (Loki Castle Hydrothermal iN-situ Experiements and Surveys) project examining hydrothermal fluid circulation at Loki's Castle vent field. The project is led by PI Thibaut Barreyre at the Centre for Deep Sea Research, Department of Earth Science, University of Bergen, Norway. A total of 8 ocean bottom seismometers (OBS) were deployed near Loki's Castle vent field at the Mohns-Knipovich Ridge bend, Norwegian-Greenland Sea. The aim of the experiment was to monitor seismicity related to changes in the hydrothermal circulation system and to reveal interaction between an active detachment fault and the axial volcanic ridge hosting the vent site. The network consisted of 8 DEPAS Lobster type broadband OBS from the German Instrument Pool for Amphibian Seismology (DEPAS). Instruments were free-fall deployed and spaced by about 5-8 km. They recorded continuously at 100 Hz for 12 months between July 2019 and July 2020. Two instruments (LOK01 and LOK06) could only be deployed one month later and recorded at 250 Hz. OBS positions at the seafloor were determined by interpolation at 2/3 of the distance between the deployment and recovery position at the seafloor. Position accuracy is estimated to be about 100 m. Skew values were obtained for all stations and reached values of up to 24 s. Clock drift in this experiment was nonlinear. Skew-corrected station LOK02 served as reference station to obtain the clock drift of all other stations using noise cross-correlation and subsequently correct also for the thus determined nonlinearity of time drift. Waveform data are available from the GEOFON data centre, under network code 8M and are embargoed until July 2025.