Zagato's younger brother and knight of unique tanlent, that figths with a sworld and a hell horse.
Lantis appears in the second part of the story. He's quiet, proud and self-confident, and these aspects of his presonality make him a person that usually is avoided from the others, but he has a golden heart and the proof is his desire to destruct the system of Sephiro. It's not just because his brother Zagato died with his beloved princess Emeraude, but because it's not right that just one single person needs to do a sacrifice in order to save all the people of that world.
Lantis' desire is to destruct the Pillar System of Sephiro, and this is the reason why in a first moment he decides to fights against Hikaru, Umi and Fu. But knowing better the girls he understands that they share the same goal and they become allies. So he falls in love with Hikaru and their relation becomes more intense day by day, especially in the anime, where we can see a real, reciprocal and deep love.
It's ironic but Lantis falls in love just with the person that will become the new Pillars of Sephiro, Hikaru, just as his brother did with Princess Emeraude. When Lantis realizes it, he really totally understands the feelings of his brother and finally he can't stop to think that he was insanity and blind for Emeraude.
His friendship/rivalry with Eagle is an important side of him, because is thanks to the sacrifice of his friend if Lantis and Hikaru can survive and change everything in Sephiro at the end.
Lantis' devoted fairy, Primera, is in love with him since always and she's very jelous of him, but at the end she undertands Lantis' feelings for Hikaru and even if it's sad for her, she accepts that only Hikaru is able to take care of Lantis' heart. A profe is that Lantis gives his beloved pendant (memory of his mother) to Hikaru before the final battle, an object very important for him.
However, the relation between Hikaru and Lantis is a bit different in the anime and in the manga.
In the anime she loves only him at the end, but in the manga she decides that she'll marry him and Eagle, both of them... I'm not that happy of this version, err... >.>"
In Tsubasa Reservoir Chronicle he has the power to see the future in his dreams (the same of Sakura-chan) and he appears in the Chess-match against Sakura's team. Unluckily, his role in that story is limited and his apparitions are a few.