On “Lost Souls,” from his new mixtape, Beware the Book of Eli, the South Florida rapper Ski Mask the Slump God draws from the sinister side of Greek mythology. “I’mma drown a nigga in a river of lost souls,” he spits over the track’s foreboding beat, threatening to extinguish his enemies in the fabled tributary of the afterlife. Call Ski Mask the hip-hop Hades—king of the underworld and the dead, god of wealth, making songs that could soundtrack the valley of directionless spirits. This is murderous, netherworld music that you can throw up your jewels and smoke a blunt to.

Beware the Book of Eli is the finest showcase so far for Ski Mask’s significant strengths. Of the 13 songs here on the leaked version (an official version, with only ten songs, was later released), only one, “The Bees Knees,” reaches the three-minute mark. This might suggest a scattershot approach, but it’s the lack of wasted motions that make the tape such a savage trip into cracked psychedelia, surreal humor, and straight-up weirdness. There’s desolation in its DNA, yet Ski Mask—an MC who in his best Raoul Duke bucket hat traverses the twisted universe ruled by God Emperor MF DOOM—dilutes that darkness with stoner absurdity. On “Ski Meets World,” he references “Bob the Builder” and Froot Loops mascot Toucan Sam, then vividly describes a sex act, veering in and out of a wacky voice that could’ve come straight out of an Adult Swim cartoon. On a track with the lurid title “Bukakke,” he envisions himself as a vampire who’s invincible to the sun’s rays. Each image is shrouded in the purple haze of weed smoke.

Ski Mask’s consistently off-kilter rap style adds to the tape’s malevolent vibe. His flow is like a butterfly sword, swooping in from a dozen directions at once and slicing from seemingly impossible angles. The frequency with which he changes up his voice might be dizzying or tiresome from a lesser rapper, but Ski Mask never loses control of his gravelly larynx. There are occasional shades of Migos’ rapid-fire couplets on Beware the Book of Eli, underlined by how easily Ski Mask’s style meshes with Offset’s on “With Vengeance.” He negotiates the skyscraper-sized bassline of “Dapper Dan” by speeding up his flow. On the warbling “Suicide Season,” his voice is melodic but bugged out, as though he’s the last conscious person at the party as the sun comes up and the smoke starts to clear.

Key to Ski Mask’s artistry is his identity as a student of hip-hop history. He repurposed Missy Elliott’s “She’s a Bitch” in last year’s “Catch Me Outside,” a number that united 1990s rap with modern street sounds. On the new tape, “Worldwide” boasts the kind of explosive beat Missy could easily have turned into an MTV smash two decades ago, underpinned by fizzing electro production that recalls early rap classics such as Afrika Bambaataa & the Soulsonic Force’s “Planet Rock.” Meanwhile, the cold production on “Throwaway” would easily fit into the 36 Chambers.

Despite most tracks’ brevity, Ski Mask finds room to toss in some choruses. The catchy hooks of songs like “Throwaway” reveal another facet of his artistry and imbue the release with enough good vibes to soundtrack a nighttime drive in a car packed with friends. But even when the music is at its liveliest, the mixtape feels cracked and decayed like a cassette left behind by a lost civilization. A brutal odyssey that nonetheless provides plenty of kicks, Beware the Book of Eli stands as a new monument on the off-mainstream rap landscape.