His rise to prominence came about by way of initially collaborating with his brother Bart under the moniker Subsphere. Together they released a number of well-regarded tracks, and releases on labels such as Green Martian and A State of Trance. Going solo in 2005, Leon produced a staggering amount of tracks and remixes while simultaneously honing his craft as a hard-working DJ with a knack for reading the floor. After joining forces with the Spinnin' sublabel 2Play in 2006, Leon would put out 20 tracks with the label over the next three years. His first full-length, Pictures, dropped in 2008. A two-disc set containing 24 tracks and numerous collaborations, including Simon Binkenborn, Jonas Steur, and Sied van Riel, among others, the album garnered praise for its breadth of influences and willingness to push the boundaries of what trance music could be, most notably the standout single Ocean Drive Boulevard, although the album also spawned the singles "Thug," "XD," "YE," and "Acapulco." These releases would cement Bolier's place at the forefront of the Dutch trance reboot, and would help him make DJMag's 2008 list of the Top 100 DJs. 2009 saw him make the list again, but this time he'd risen 32 places to number 68. Bolier would continue to put out tracks at a rate of almost one a month, as well as playing hundreds of shows a year, culminating in his follow-up album, 2010's Phantasma. Once again the album spanned two discs, and was released on Bolier's own label, Streamlined Recordings, a sublabel of Spinnin'. The album drew praise for providing the expected big-room floor-fillers as well as more expansive and imaginative tracks, and featured a whole host of collaborations with artists such as Alana Aldea, Marieke de Krui, and once again, Sied van Riel, among others. By the time 2011 had come around, Bolier's direction in music had changed somewhat, as illustrated by the electro and progressive leanings of tracks such as Disco Davai. 2015 saw Leon adopt a new moniker, WSTLNDR, and with it came a return to his trance roots à la Phantasma with the release in September 2015 of his third album Atmostopia. The album was billed as a display of the producer's unchained creative freedom from the need to produce conventional dancefloor music. Released on the one-time DJ Tiësto-owned Black Hole Recordings imprint, the album eschewed the multitude of featured artists found on his earlier releases, and instead utilized a deeper set of sounds, effects, and textures to transport the listener to places other than the nightclub. ~ Simon Spreyer