Abstract: Various examples are directed to a multistage refrigeration system comprising a vapor compression cycle (VCC) stage, a thermosiphon stage, and an interface device. The VCC stage may circulate a VCC refrigerant, for example, to work a vapor compression cycle on the VCC refrigerant. The thermosiphon stage may circulate a thermosiphon refrigerant between the interface device and an evaporator. The interface device may comprise an interface flow path in fluid communication with the VCC stage to receive the VCC refrigerant and a first vessel that at least partially encloses the first interface flow path. The vessel may receive the first thermosiphon refrigerant at least partially in a vapor phase and may provide the first thermosiphon refrigerant to the evaporator at least partially in a liquid phase. The vessel may be at a second elevation, higher than the first elevation, to generate a thermosiphon force to circulate the thermosiphon refrigerant between the vessel and the evaporator.