Chronolith Trials are a side activity in Final Fantasy XVI. They are stone monoliths that take you to a trial level where you can test your mastery of a specific Eikon. Here you can find them all.
Final Fantasy 16 (XVI) – The Hand of Hyperion (Phoenix) Chronolith Process
There are seven Chronoliths in Valisthea, and eight if you've purchased The Rising Tide DLC. Each Chronolith Trial tests your mastery of a specific Eikonic power that you possess. You only need to complete the first seven to unlock the For the Hoard trophy, one of the must-have trophies in Final Fantasy 16.
To find the Hand of Titan, first teleport to the nearest obelisk, the Velkroy Desert. From there, head north to The Northern Velkroy Desert. You'll pass the abandoned town of Ceratina; look for a passage that will lead you to an isolated area populated by a few small monsters. Defeat them to unlock the Hand of the Titan Chronolith Trial.
Related: All Eikons Are Missing in Final Fantasy 16