Authors: Tingyu Gou (CfA), Katharine K. Reeves (CfA), Peter R. Young (NASA GSFC)

We present observations of an intense and long-duration but confined flare that occurred at the solar west limb. The event was simultaneously observed by various instruments including the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO), the Interface Region Imaging Spectrometer (IRIS), the X-ray Telescope (XRT) and the EUV Imaging Spectrometer (EIS) on Hinode, and the Spectrometer/Telescope for Imaging X-rays (STIX) on Solar Orbiter. A prominence rises at the limb in the initiation phase, but finally fails to escape from the Sun with plenty of material falling back. A magnetic flux rope structure that rises together with the prominence contains high-temperature plasmas as is evident in XRT and AIA hot channel images. During the gradual phase of the flare, large-scale loops and a cloud of diffusive plasmas in high temperatures stay at high altitudes above the post-flare arcade, which are visible for more than four hours. Taking advantage of the multi-messenger and multi-wavelength observations, we investigate the plasma emission and flare dynamics during the unorthodox long-duration confined event.