Baldur's Gate 3 is full of secrets. The Mind Archive Interface is a hidden interaction that is only possible at the end of Act Two and only if you have collected the right items during the campaign.

After you enter the Mind Flayer Colony following your first encounter with Ketheric Thorm, you'll have the rare opportunity to explore the Mind Flayer base. The Mind Archive Interface can provide some interesting information about the Absolute, the Mind Flayers, and the Colony. If you're trying to find or use the Mind Archive Interface in Baldur's Gate 3, here's what you need to know.

You cannot reach the Mind Archive Interface until after you enter the Mind Flayer Colony at the end of Act Two. Travel to the Necrotic Laboratory in the Mind Flayer Colony, located beneath the Moonrise Towers. You can access the Mind Flayer Colony after you first confront General Ketheric Thorm atop the Moonrise Towers. He flees there, wounded. The Mind Flayer Colony is located beneath the towers, and can be reached by entering the hole that spawns after you defeat Ketheric Thorm for the first time.

Once you reach the Necrotic Laboratory, defeat Death Shepard and his minions. The easiest way to defeat Death Shepard is to target him before attacking his minions. If you leave him alive, he will revive his minions and the fight can get out of hand. I usually try to AoE his minions and send one of my tankiest characters (Lae'zel or Karlach) to take out the Shepard.