The big draws for ToME (for me) are: character classes, challenge, and music.
The game really has some cool classes, more complex than I’ve seen in any other Roguelike (and I’ve played a lot).
For example, the solipsist is a psionic character who grows more and more powerful mentally but more and more frail physically. They gain the power to warp the shape of reality with your mind, projecting waves of force and even creating swirling maelstroms of distortion.
They also gain the ability to sear the minds of their enemies, to project your own mind outside their body and travel through walls, to put all of their enemies to sleep and make their nightmares come alive to attack them, and even invade their dreams to destroy them in the dreamscape.
Another class, the paradox mage, is the master of time and space, with control over gravity and matter. They can create gravity wells, materialize barriers of solid matter and then blast them apart, create spikes of locally intense gravitation that rip through enemies. Create wormholes and warp mines to teleport themselves and enemies around, or dimensionally anchor enemies so that they snap back to where they were if they try to teleport (or are forced to teleport) away.
They can create temporal clones to fight alongside themselves, or travel into an alternate timeline to destroy an enemy, erasing them from the current timeline and continuing as if your target never existed in the first place. They can even stop time or take themselves out of the flow of time altogether. As well they can place a spell on contingency, having it cast automatically when their health drops below a certain threshold.
Perhaps their most dramatic talent is the ability to peer into the future and play out three different timelines, and then choose which of the possible futures becomes your reality.
And that’s just two of the many classes. There’s tons more and they all play completely differently from one another!