A Vulcan puzzle game in which players place small rods called t'an to turn a chaotic tangle into an ordered shape, played aboard Voyager by Tuvok.
Kal-toh is played with a heap of thin metallic rods. Each move adds a rod, and the aim is to find the positions that make the disordered mass resolve itself into a perfect geometric form. Tuvok says it is about finding the seeds of order in chaos and that comparing it to chess does it little justice.
The game is introduced in the Voyager episode Alter Ego, where a holodeck character who plays it suspiciously well turns out to be a lonely alien watching the ship. Tuvok teaches Harry Kim, and in The Omega Directive Seven of Nine casually completes a position the two have been studying.
In Endgame, Icheb defeats Tuvok, an early hint that the Vulcan's mind is beginning to fail from a degenerative illness.