The son of king Oeneus, exiled prince of Calydon, and father of the mighty Diomedes. Originally the heir to the throne of Calydon, Tydeus had a fight with the oldest of his siblings, Meleager to see which one would search for heroes to stop the Calydonian Boar. While Meleager was the one who started the fight, Tydeus was the victor, and nearly killed Meleager. However, his father judged him guilty, and banished him from Calydon. Seeing this unfair trial, Athena descended from the Olympus, gave him arms bearing the image of the beast that ravaged his father’s kingdom, and told him that he should go to Argos.
In Argos, Tydeus was welcomed by king Adrastus, who was also housing Polynices, son of Oedipus, who had been banished from Thebes by his brother. At night, the two exiled princes battled to see which one would sleep at the guest room in the palace. Seeing the two young warriors fight, Tydeus’ equipment bearing the image of a boar, and Polynices’ bearing that of a lion, Adrastus remembered the prophecy that said that he should marry his daughters to a boar and a lion. Thus, Tydeus and Polynices became princes of Argos.
Adrastus promised to both princes that he would help them take over the kingdoms that were rightfully theirs, starting with Thebes. Adrastus arranged to raise seven armies from the region surrounding Argos, each army led by a mighty hero, and thus originating the Seven Against Thebes, the largest army that had ever appeared in Greece.
Shortly after the Seven arrived in Nemea, the young son of the Nemean king was killed by a snake. Adrastus ordered his man to kill the snake, bury the boy, and hold the first Nemean Games in his honor. In these games, Tydeus proved his unarmed skills by winning the boxing event without a single hit being landed on him.
After the armies reached Kithairon, Athena appeared to him again, gave him the star-bearing shield, and explained that, as long as one man was spared, he could deal with an entire army at once. He was sent to Thebes before all others, to demand that Polynices was reinstated as king. The Theban king and Polynices’ brother, Eteocles, ignored Tydeus, and enraged, Tydeus challenge multiple Thebans for one-on-one combat, defeating every single one of them easily. When he was returning to Kitharion, he was ambushed by a group of fifty Thebans, but managed to kill each one of them, except for one, Maeon.
After the armies reached Thebes, each one was sent to attack one door, with Tydeus being responsible for the first door. In battle, Tydeus was quite the monster, tearing apart anyone who tried to defeat him. The Thebans sent Melanippus to fight against him, and, while he managed to kill his enemy, Tydeus had been mortally wounded. Athena, seeing her champion half-dead, descended from the Olympus again, this time to give him an elixir that would grant him immortality. However, blinded by rage, Tydeus crawled towards Melanippus’ body, and, like a savage, devoured the Theban’s brains. Disgusted with this sight, Athena retreated, and kept the elixir hidden, which would, years later, be used on Tydeus’ son, Diomedes.
As a Lancer, Tydeus behaves calmly when outside of battle, almost in a gentlmanly way. Yet in battle, he becomes a brutal warrior who enjoys nothing more than seeing the remains of his enemies spread across the floor. As a Berserker... well, he's a berserker.
His wish for the Grail would either be A. Have a chance to beg Athena for forgiveness for the monstrous thing he did to Melanippus' corpse, or B. Summon the other six leaders and go conquer modern-day Thebes. And after that, all of Greece, maybe.