There are several artists named Mourn:
1, A post punk band from Spain
2. A doom metal band
3. A black metal project from the United States

1) 'Mourn' is a quartet from Maresme, Barcelona, formed by Carla Pérez Vas, Jazz Rodríguez Bueno, Leia Rodríguez and Antonio Postius. They were signed to Captured Tracks in 2014 after they uploaded a live studio recording of Your Brain is Made of Candy. The 10 track debut LP, 'Mourn', was recorded live in the studio in two sessions and released in late 2014 (digital) and February 2015 (physical). It features Otitis and Silver Gold. Their second LP, 'Ha, Ha, He.', was released on June 2016 also via Captured Tracks. it includes Evil dead, Storyteller and Second Sager.

http://www.capturedtracks.com/#!mourn/zwrbj

2) A Doom Metal band fronted by Caroline Wilson. They released the demo 'For Evermore' in 1993, and their debut album 'Mourn' in 1995 through the label Rise Above. It contains the track 'Children of the Circle'. The album was re-released in 2007.

3) Mourn is a one man black metal/doom metal/dark ambient artist from Seattle, Washington.

www.mourn.bandcamp.com