Cruel Trials Of Ascendancy Locations
In Cruel difficulty, you will revisit and find new trials. Here are the locations:

Act Six:
The Prison: The trial can be found in the updated version of the Prison in Act Six.
Act Seven:
The Crypt: The Crypt trial reappears in Act Seven, requiring you to navigate its depths.
The Chamber of Sins: Visit the Chamber of Sins in Act Seven to complete the trial there.
Act Eight:
The Bath House: A new location for the trial in Act Eight. Explore the Bath House for the trial’s entrance.
Merciless Trials Of Ascendancy Locations
The Merciless difficulty introduces new locations for trials:

Act Eight:
The Bath House: Located here again, but in the updated Merciless difficulty.
Act Nine:
The Tunnel: Find the trial within the Tunnel area of Act Nine.
Act Ten:
The Ossuary: This area will have the final Merciless trial, located in the Ossuary of Act Ten.
What Is The Eternal Labyrinth?
The Eternal Labyrinth is the ultimate labyrinth challenge in Path of Exile. Unlike the other labyrinths, it does not become available simply by completing trials. To access the Eternal Labyrinth, you need an Offering to the Goddess. This item is crucial for entering this final challenge and is usually obtained through various in-game methods or trades.

The link (https://www.mmoexp.com/Path-of-exile/Currency.html) leads to additional details about the game.