Tool played the first of two nights at the Pepsi Center on Tuesday, October 15.

Four hours after Tool finished its two-hour show at the Pepsi Center, I couldn't fall asleep. I felt like a massive octopus was wringing out my brain. Flashbacks from the sold-out concert swirled through my head, and the ringing in my ears echoed the thud-thud-thud of subwoofers that had rattled my gut and chest.

I thought about that massive sheer curtain that surrounded the stage the first half-hour of the concert, which would occasionally open and close throughout the set. While the band was visible, the fabric created a shroud of secrecy, like maybe these guys had something to hide. Or maybe they didn’t have gigantic egos. Or they just wanted a force field between them and the crowd.

During that first half-hour, the curtain made me anxious: “Is this thing going to be up the entire show?” I was relieved when the glimmering see-through curtain was pulled back and the band could be seen more clearly.

Frontman Maynard James Keenan looked like some punk-rock warlord from another planet, with his mohawk, red plaid pants, leather motorcycle jacket and boots. He spent most of the show on platforms on either side of Danny Carey’s drum riser. Keenan didn’t strut his shit all over the front of the stage. He hung out on the platforms, sometimes crouching like a caged panther, other times just singing at the mic stand. He was there for the music, not the theatrics.

It was the same thing with guitarist Adam Jones and bassist Justin Chancellor, who pretty much stood by their pedal boards the whole show. They seemed hyper-focused on the push and pull of Carey’s odd-time signature drumming.

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While the crowd ate up the new material from Fear Inoculum, the band’s first album in thirteen years — like the title track, which opened the show, and “Pneuma,” the crowd went nuts for the second cut of the night, “Ænima,” prompting a kid who looked like he was about ten years old to pump his arms and throw up the devil’s horns with his fingers, the first of many such gestures.

During “Fear Inoculum,” trippy psychedelic imagery was projected on a massive screen behind the stage. But “Ænima” was accompanied by animations of what looked like aliens. Or skeletons. Or alien skeletons that had some sort of internal organs.

Tool delivered an insanely muscular set, but the video projections created a surreal experience.

At one point, the screen showed someone getting a hardened artery extracted from his neck — a blood branch, which dissolved when it fell on the floor. During “Vicarious,” where Keenan was singing through a bullhorn, there was a video of a fetus inside a skull. And in another video, a guy looked like he had a cord coming out of his neck.

While trying to sleep after the show, I kept thinking, “Why the fuck was that cord there?”

Before the concert, there were announcements about the strict no photo/video policy during the show, but before the final song, “Stinkfist,” Keenan told the audience they could shoot it. Keenan, who hardly talked between songs, also thanked guitarist Brent Woods for shredding.

Woods, who studied with Ozzy Osbourne's guitarist Randy Rhodes, took a solo during “Jambi.”

“A guitar solo at a Tool concert?” one guy asked.

Indeed, Jones didn’t spend much time shredding during the show. But he didn’t need to. The music was powerful as it was — even if it kept me up all night.

Tool performs another sold-out show Wednesday, October 16, at the Pepsi Center.