Jaden Yuki (Judai Yuki in JP) is the main protagonist in Yu-Gi-Oh! GX, the second anime in the Yu-Gi-Oh! series. His main ace card is Elemental HERO Neos, a normal monster with attack and defense similar to Yugi's Dark Magician. It's specialty is having multiple different fusion monsters using the Neo-Spacians, resulting in over 10 different combinations.
To unlock Jaden Yuki, you have to achieve a mission: Summon Warrior-Type Monster(s) 10 time(s) in total. Once you claim the reward for the mission, "Complete all Character Unlock Missions" is also achieved. Winged Kuriboh is a reward for the mission, and now you unlock Jaden Yuki as a playable character!
Where the Heroes Dwell Can be used after you Life Points are 2000 or below. Play the Field Spell "Skyscraper". If there already is Field Spell on your side of the Field, Return it to your hand. This skill can only be used once per duel.
Fusion Time! Can be used each time your Life Points decrease by 1500. In the Draw Phase, instead of doing a normal draw, Polymerization spell card, from outside of your Deck, is added to your hand.
Reinforcement Can be used each time your Life Points decrease by 1800. Return 1 card from your hand to your Deck and draw a random Warrior-Type monster.
Miracle Fusion Time! Can be used if your Life Points drop below 500. In the Draw Phase, instead of doing a normal draw, Miracle Fusion spell card, from outside of your Deck, is added to your hand. This skill can only be used once per Duel.
The Tie that Binds Until the end of you turn, the ATK of all face-up monsters on your field increases by the number of monsters on your field times 100. This skill can only be used once per turn.
Grit The skill is activated randomly when your turn starts. Your Life Points does not get decreased to less than 1 until your opponent's next turn ends.
In the anime/manga, Judai uses elemental HERO deck. They are very focused on fusion summoning. Using Elemental HERO Neos, a level 7 normal monster and also his main signature card, it can fuse into more than 10 different fusion monsters using other elemental/hero monster cards, above are some examples of it. List of "Elemental HERO" cards
His other potential signature card is Yubel. A main antagonist in one of the show's arcs, but later became part of Jaden by fusing together, resulting in a similar relationship like Yami Yugi is to Yugi Muto. Yubel is also an archetype, having multiple supports and revolves around destroying Yubel to be able to summon other monsters.