This is considered to be easier than the first Jack of Blades fight in the Chamber of Fate, but can be frustrating if you don't know what you're doing. A good tactic is to use the experience gained from The Souls of Heroes to max out Strength and the remainder to raise the Hero's Speed.
There are several credible methods to defeat Jack of Blades:
This method causes less damage to Jack's health, but he will also inflict less damage upon you. If you have a high range specialty or you're a good mage - keep running around the arena while hitting him in the nose with Fireball, Lightning or even Ghost Sword if you must.
This is a good melee technique and takes a lot of health from Jack in a short period of time. If you can activate Slow Time just as he lands, it will sometimes end exactly when he takes flight again. If you have a really strong weapon like the Solus Greatsword or Avo's Tear, his health meter will go down incredibly fast.
Multi Arrow comes in very useful here, and this is especially powerful if you have it at a high level with a legendary bow. Simply stand on one of the podium-like perches at either side of the triangle and shoot him when he lands. Avoid his fire, and when a Summoner comes, destroy it - or better yet, bait it into Jack's own fiery breath. Repeat this, occasionally stopping to use a potion or the Heal Life spell until he's dead. This method requires a little patience, but it is a very safe method for defeating him.
The fastest, and most dangerous, way of doing this is to use a combination of Berserk and Physical Shield, as long as both of them are past level 4. Make sure you have a lot of potions because you need to make sure Physical Shield is always up. Use Berserk right before he drops from the sky and repeatedly hit him between the eyes. If the Hero's Physique is maxed out Jack can be killed within the first four times he lands.
Even faster, use Berserk first and then use Multi Strike continuously until Jack is dead, he will die in just one or two times of landing.
You will need a high-level Multi Strike spell and Slow Time spell (at level 3 or 4). As the battle begins, cast Slow Time then run up to Jack and start hitting him with Multi Strike, repeating the spell. He will lose a lot of his health quickly if the Hero has maxed out Physique.
When the Hero eventually kills him, he will absorb Jack's soul into his mask and the player will be presented with a choice - wear the mask or throw it into the surrounding lava. Scythe will contact the Hero and demand that the mask be thrown into the lava, while Jack tempts the Hero to wear the mask with promises of great power. If the player chooses to wear it Jack will take over the Hero's body, killing him in the process, but the soul of Jack of Blades will live on. However if the Hero casts the mask into the lava, the soul of Jack of Blades will be banished from Albion forever.