Nicholas Arkham

Her research focuses on botany (the study of plants).
She keeps records of the birthday party thrown for her by the other Seekers, and their portraits - perhaps she still has some feelings for them.
Connection with Ambrose Armitage. The characters had a close relationship:

Isadora gave Ambrose a framed picture of his favorite zodiac sign, the Oathbreaker.

Ambrose's notes feature Isadora's favorite zodiac sign.

Isadora Waite
Isadora studied stars and their formation processes. Her scientific work was part of the Seekers' broader research aimed at understanding supernatural forces.
Connection with Ambrose Armitage. The characters had a close relationship:

Isadora gave Ambrose a framed picture of his favorite zodiac sign, the Oathbreaker.

Ambrose's notes feature Isadora's favorite zodiac sign.

Fair skin, brown eyes, and light hair. There's a scar on her neck that resembles a star.

She wore a blue plague doctor costume, which was the main part of her image.

Plague doctor mask - complements the costume and matches the style.

The blue top hat is an element of the headdress in the ensemble.

Glasses - used for detailed examination of objects.

Studies technology

She has fair skin, light eyes and light brown hair.

Nicholas Arkham is a scientist and researcher. His field of study is alchemy: he focuses almost entirely on creating potions and conducts experiments in a special laboratory room. To collect data, Arkham creates numerous miniature robotic dolls—replicas of himself—that spy in dangerous areas, allowing him to avoid direct contact with the threat. His image includes:

plague doctor mask;

hat;

a very long yellow jacket with markings;

cape;

dark trousers with yellow edges;

brown boots;

gloves
Handwriting: illegible, which may indicate haste or peculiarities of thinking.

Left-handed: presumably uses the left hand

He has more or less dark skin, brown hair and blue eyes.