Kaunan

Kaunan is a Jotun of fire and lava, who wields an immense sword. A skilled blacksmith, he is the forger of the blade of Ragnarök and may be the father of the molten giants encountered in the Crater. His namesake is the rune representing the torch, mortality, and pain. He is the Jotun associated with Muspelheim (Ymir's Blood and the Crater) and the fifth Jotun Thora fights, assuming you follow the order suggested by the game.

Attacks

 * Kaunan's basic attack is an overhead swing of his sword, denoted by a shadow. After executing it, his sword will become stuck in the ground, allowing to score some hits on him. The attack has a long reach, but very little width, making it one of the easiest basic attacks to avoid of any Jotun. However, it also deals enormous damage.
 * After taking a lot of damage, Kaunan falls to the ground and becomes vulnerable. However, if he falls on you he will push you back, potentially into hazardous areas. His helmet is a weak point, and attacking it deals significant damage to Kaunan.
 * Upon losing some health, Kaunan starts jumping high in the air. The location of his landing will be marked by a shadow, and if he lands on you, expect tremendous damage. He remains vulnerable for a few seconds after using this attack. His landing causes multiple meteors to fall from the sky (also marked by shadows), which deal contact damage and also leave behind temporary burning patches that cannot be crossed without taking damage.
 * Occasionally, Kaunan will move out of range and trace a circle in the ground with his sword. This will send multiple cracks through the ground. They erupt into flames after a brief delay.
 * At about half health, Kaunan's rage reaches a boiling point as he unleashes the full power of his flames. A massive rain of meteors will sweep the arena at this point, turning much of the terrain temporarily unsafe. In addition, Kaunan will empower his attacks so that both his sword swing and his jump will cause erupting cracks in the ground upon impact, while the cracks produced by his circle become much bigger and more dangerous.

Strategy
During the battle against Kaunan, the most important factor is being aware of the flaming patches left in the ground by his meteors. Notably, the knockback induced by him falling on you can easily propel you into those patches and inflict major damage.

By far his most dangerous attack is his jump. The impact zone can be difficult to get out of before he lands, and the subsequent meteors are the primary danger in the battle. However, since Kaunan becomes immobile for a few seconds after landing, it can be a good moment to smash him, provided no meteor is headed your way. Note that at low health, Kaunan can start doing three jumps in quick succession.

As long as you remain vigilant, his other attacks are usually not difficult to avoid due to their small width.

Freyja's Speed can be helpful to avoid his leaps, especially the three leaps in a row.