SPOILERS FOR BALDUR'S GATE 3 FOLLOW
Over the course of Baldur's Gate 3, you'll encounter multiple elements of the previous two games in the series including locations and characters such as Jaheira. Later in Act 3 of the game you can also encounter a legendary figure from the previous two games in the series, Minsc, but you have to hunt him down.
Where To Find And Recruit Minsc
Minsc can't be found until Act 3 of the game and requires that you keep Jaheira alive throughout Act 2. Once you hit Act 3, and assuming Jaheira has joined your party, she'll issue you with a quest that will send you around all of the Lower City in an attempt to find her friend. To find Minsc you need to make it to the Abandoned Cistern in the sewers before solving the puzzle that faces you there.
In order to solve this puzzle you just need to do the following:
- Use the Water Valve on the left and wait until it says 'Perfect Water Level'
- Use the Heat Valve
- Once the Heat Valve hits 'Perfect Warmth' the Sluice Gate will open
Once you travel through the Sluicde Gate you'll encounter a cutscene that reveals some shocking twists and turns that we won't spoil here. What's important is that you'll be thrust into a fight with Minsc and a gang of other people, and you NEED to make SURE that you use a non-lethal attack to take Minsc out so that you do not kill him, else Jaheira WILL leave your party.
Once you've completed that battle you'll be told by the Emperor Mindflayer to just leave him, but it's up to you to tell him to extend his protection against the Absolute to Minsc. Once you do, Minsc will run off and start breaking down walls. As it turns out, he's looking for his hamster, Boo, and the pair can now join your party.