Larian Studios Forums Baldur's Gate III Baldur's Gate III - General Origin Character's Myers-Briggs Type

Tertiary functions are interesting because this is the behavior that comes out when something’s a little off with the way they are thinking or interpreting a situation. It's how they can be convinced of something they'd normally not entertain. It can very much hint the direction possible redemption arcs might entail. This is also where their most immature behavior comes from: Lae’zel’s brattiness, Astation’s cruelty, and Shadowheart’s mixed messages. Also, I personally wrestle with Tertiary Fi and am very accustomed to it, so I very much relate to this aspect in LZ and SH. When it comes to ISTJ and INTJ, people are often very surprised at the emotions that lurk buried beneath.

Lae’zel Fi Tert
Decisions primarily made by how well they fit into her understanding of how the world works and involves an element of emotional suppression. Things are good and right based on how well she is operating as an essential cornerstone of a more stable whole – as a model Githyanki.
However when challenged and pressured, decision making can bypass her understanding of how the world works. Instead it revolves around the sense of inherent worthiness or unworthiness [Fi] she can internally feel [Si] - derived from the information she holds in mind. When things don’t add up, it’s someone else’s wrong doing at best or her ultimate failure at worst.
There is an element in Fi being tertiary that involves self-doubt and putting all your trust in an external system. This is what you’re seeing any time she looks unsure as well as the anger in the aftermath of the Gith Patrol. Furthermore, eventually coming to terms with the inferior function can allow a stronger sense of self without needing an external system as a crux.
Appealing to her sense of worthiness is a path she can be persuaded to deviate from usual trains of thought.

Astarion Te Tert
Decisions primarily made by how good things play out, how pleasurable and exciting they are, and involves an element of rationalization within an understanding of how the world works.
This can make desires more realistic and easier to obtain, but when challenged or pressured, decision making can bypass what he normally tolerates.
If the entire world is a vile place and all he’s ever known or expects, then basically anything goes. Giving into bloodlust, being at the mercy of his own whims, and maneuvering the world in a way to do as he pleases are rationalized away as the right thing, despite any personal or emotional reservations he might have or once had.
When things are boring, he has to make his own fun – often at the expense of others.
Convincing him of different ways to interpret the world is a path he can be persuaded to deviate from usual trains of thought.

Shadowheart Fi Tert
Again, Decisions are primarily made by how well they fit into her understanding of how the world works and involves an element of emotional suppression.
Things are good and right based on how well her intuitions formulate a cohesive picture of how the world works. However when challenged and pressured, decision making can bypass that understanding. Instead it involves the sensations that linger after the intuition is felt.
What she senses can often immediately reinforce how she feels, and make it seem like anything other than what she has sensed will cause her to lose her footing. This can involve hair trigger reactions to what is more an internal sensation than what is really occurring, and cause her to obscure or suppress it as a defensive mechanism.
When things don’t add up, there has to be something she’s not seeing. There has to be something more going on.
Again, there is an element in Fi being tertiary that involves self-doubt and putting all your trust in an external system. And in Shadowheart, that manifests as her emotional relief found in Shar worship and a sense of relief in beleving it good to not care/turn a blind eye to the suffering in the world – as if it was once too great a burden to bear. Appealing to her deeper emotional sensations is a path she can be persuaded to deviate from usual trains of thought.