Since their inception in 2016, British band Sleep Token have established themselves as one of the heavy rock world's most unique entities. Driven by the mission to project the message of the deity known as Sleep, whom singer Vessel encountered in his dreams, the group wear masks, cloaks and black body paint to anonymize themselves — emphasizing that it's the art that matters most.

Sleep Token — Vessel, drummer II, bassist III, guitarist IV, and vocal trio Espera — write their own rules of what heavy music can be, avoiding cliches and stereotypes with lyrics that address highly personal subject matter. Their music is not always literally heavy, either; sometimes the heaviness comes through the feelings expressed, and it's more hypnotic than hyperactive. No matter the sound, the pure emotion expressed through Sleep Token's vocals and music has engaged a massive, passionate fan base. And two years after their last album, 2023's Take Me Back to Eden, the band is unveiling what could be one of rock's biggest releases of the year.

Even In Arcadia, Sleep Token's fourth studio album and first for RCA Records, already proved how their following has grown — and how the mainstream is catching up — before its May 9 release. Along with landing the group's first entries on the all-genre Billboard Hot 100 chart, the album's first three singles helped Sleep Token make history on Billboard's Hot Hard Rock Songs tally with three No. 1s in a row.

Despite growing mainstream success and the pop influence in their catalog, Sleep Token has never pandered to overt commercial tastes. They usually shirk the standard verse-chorus trade-off typical of hit songs; shifts in dynamics are common during their often sprawling, multiform compositions. Even In Arcadia expands on their boundary-pushing sound, from a soulful sax solo ("Emergence") to effortless genre transitions ("Gethsemane" flows from pop to metal to atmospheric trap). Vessel even displays a matured sense of self-awareness on "Damocles": "I know I should be touring/ I know these chords are boring/ But I can't always be killing the game."

This unconventional approach to songwriting and blend of musical styles has drawn a legion of devoted fans, including famous rockers like Slipknot's Corey Taylor, Evanescence's Amy Lee and Linkin Park's Mike Shinoda. As indicated by their recent chart success and sold-out fall arena tour, Sleep Token's allure is engaging more and more listeners — and at a rapid pace.

For the uninitiated, here are five enigmatic Sleep Token tracks to begin the journey into their realm.

The most popular song in the band's live set, "Alkaline" begins with a music box-like keyboard pattern juxtaposed with ominous riffs. This is one of their tracks that ripples with goth undercurrents, and Vessel passionately croons over chunky riffs in a way that's distinctly Sleep Token.

Though the part that could be considered the chorus has no words, the rest of the song sees Vessel exploring the concept of having one's world (and possibly brain chemistry) altered by a serious object of desire: "She's perfectly misaligned/ I'm caught up in her design/ And how it connects to mine." This kind of emotional, confessional quality is what fans love to dissect in their lyrical analyses.

A more conventionally structured rock song in the band's canon, "Hypnosis" is a moody track filtered through a post-rock haze. While IV's guitar riff glides along midtempo, II's syncopated, polyrhythmic drumming gives it an extra kick. His percussive prowess on this song has been spotlighted by fellow players impressed with his chops.

Sleep Token don't write fast songs, but this one is propelled by an undercurrent of dark energy. II's influences span everything from gospel to drum and bass, and closes with an eerie ethereal coda. A more metallic number with a Tool-like vibe, "Hypnosis" is a good gateway rocker for people new to the band's world.

One of Sleep Token's heaviest tracks, "The Summoning" spans elegant high notes to blistering djent screams. Beyond the pummeling sections, the song itself has three distinct interludes: a jazzy guitar break, an ethereal ambient soundscape, and a slow-grinding funk outro. This is a prime example of Sleep Token's directive of diversity.

The lyrics address the uncertainty and vulnerability of being enamored with someone without knowing their full intentions. As Vessel ponders, "Did I mistake you for a sign from God/ Or are you really here to cast me off?"

For those who want to hear Sleep Token more in pop mode, "Euclid" offers a pretty piano ballad punctuated with some rocking moments. The vocal harmonies take on an alien quality through digital manipulation; that can be an acquired taste, but it clicks here. Even though the song swells to a glorious climax, it's ultimately a celebration of a fading happiness, and one that will linger for a long time.

Notably, "Euclid" closes with a stanza of lyrics from the opening track of their debut album, "The Night Does Not Belong To God," and also references "When The Bough Breaks" from their 2016 EP, One. As the closing track on Take Me Back To Eden, "Euclid" seems to mark the end of the first trilogy of Sleep Token albums — hinting that Even In Arcadia launches a new path.

While the first three singles from Even In Arcadia have already made a big impression on fans, the album's opener packs an emotional wallop from the outset. Synth strings crescendo in the intro as Vessel repeatedly queries, "Will you haunt this eclipse in me?" The song erupts into a burst of metallic fury, then dissipates into ambient solace before morphing into a harmonious trap section.

"Look To Windward" shows how Vessel and his bandmates let the emotion of the music guide the way, rather than conforming to standard structures. The angsty track's strong buildup and turbulent musical shift showcase the epic side to their music, one of the many elements that has kept Sleep Token fans old and new wanting more.