You can try the Trial of the Sekhemas in Act 2 of Path of Exile 2, after you beat Balbala the Traitor and unlock the desert caravan route to the trial area. The trial is started at the Relic Altar using Balbala’s Barya , and one guide notes you can request another Barya if you fail.

What that means in practice

  • Reach Act 2 of the campaign.
  • Defeat Balbala the Traitor.
  • Return to the caravan/desert map access point and open the Trial of the Sekhemas from the altar.
  • Use Balbala’s Barya to enter.

A useful timing note

The trial is described as the first possible Trial system you can access for Ascendancy in PoE 2, so you do not need to wait until endgame.

TL;DR

You can try it during Act 2, right after beating Balbala and unlocking the caravan’s trial access.