It would eventually take on the form of a full band as Hegnor (also of Peste Noire) and Arguth joined the fray and released a four-track demo entitled Tristesse Hivernale in 1999. This demo was a more straightforward black metal affair, much different from what would come next. After that release, Alcest returned to a one-member format, with Neige moving away from the metal overtones of the three-piece and embracing a more atmospheric approach to his work. The 2005 EP release Le Secret was more in tune with the project's ultimate goal, which was to put to ear, as it were, Neige's fascination with an "otherworld" -- of sorts -- that had held a fascination for him beginning in his childhood. In 2007, Neige released the first full-length Alcest recording, Souvenirs d'un Autre Monde ("Memories of Another World"), which was released on Prophecy Productions, and was a critical success. A split EP with Angmar was released in 2007, followed by another split with Les Discrets in 2009. In 2010, the much-anticipated full-length Écailles de Lun was released. Alcest's genre-melting renown spread across the globe with critical notices regarding the album's quality. Neige's Alcest and Prophecy Productions reissued the Le Secret EP in 2011, adding two re-recorded versions of its two songs, "Le Secret," and "Élévation," according to Neige's intentions to offer a better-produced version of the music. This new edition included drums by Winterhalter. In order to preserve the historical integrity of the original version, the 2005 EP was also included. In January of 2012, Alcest released their third full-length, Les Voyages de l'Âme.

The band moved further afield and left metal behind on their fourth full-length. Multi-instrumentalist and vocalist Stéphane "Neige" Paut and drummer Jean "Winterhalter" Deflandre enlisted producer Birgir Jón Birgisson (Sigur Rós), the string quartet from Icelandic band Amiina, and guest vocals from Slowdive's Neil Halstead. The album Shelter was issued in early 2014.

After an international tour, Alcest returned to the recording studio late in 2015. Their fifth studio album, Kodama, was conceptually inspired by the animated film Princess Mononoke; it marked a stylistic return to metal and offered a hint of the musical terrain explored on 2010's Écailles de Lune. Kodama was issued by Prophecy Productions in the fall of 2016. ~ Chris True