|Nationality||The Southern Isles|
|Hair color||Dark chestnut|
|Allies||King Klaus (eldest brother, employer)|
|First appearance||Frozen: The Kingdom of the Sun|
Prince Isak Westergaard is the eighth prince of the Southern Isles.
At first glance, Isak appears to be perpetually calm, or even half-asleep. He is usually lost in his own head with little idea of what is happening around him, and speaks in a lethargic manner with drawn-out vowels. For these traits, Isak is widely considered creepy and weird. However, he is otherwise quite friendly; Isak disregards the cruel teachings of his father King Soren, and is among the few Westergaard princes that did not maliciously bully Hans growing up, thereby earning, at most, a strained respect from the thirteenth brother.
In a clan that holds strength and power about all else, Isak stands apart as a man of science and knowledge. Outside of meals and mandatory meetings, he rarely interacts with his brothers, preferring to spend his time alone, conducting scientific experiments in a laboratory found in the palace dungeons. Isak's area of study is wide, extending from biology to chemistry to engineering. His chief interest appears to be potion-making, which often ends in explosions. Although not outright stated, it seems that Isak's "station" within the Southern Isles' government is the creation of poisons and bombs for warfare.
Unfortunately, Isak's devotion to his experiments has no sense of restraint; he considers everyone, even family members, test subjects in waiting. Hans claims he narrowly escaped Isak's attempt to perform surgery on him as a child, and upon learning of Elsa's magical abilities, Isak tries to cut off a lock of the Snow Queen's hair, presumably to use in some kind of study.
Isak is a tall and skinny man with short chestnut hair that stands perfectly on end and hazel eyes. He often appears to be sickly pale and his eyes are bloodshot and have bags underneath; these traits are likely either from lack of sleep or breathing noxious vapours from his potions.
Isak wears a dirty, off-white hooded greatcoat reminiscent of a modern lab coat, leather gloves that cover the forearms of his sleeves, no shoes, and occasionally, a white mask similar to a plague doctor's mask.
- Isak sleeps in his dungeon laboratory.
- It is implied that Isak does not wear anything under his coat.
- Isak is the sole Westergaard prince who is never shown singing, only humming.