Alex is a rival and eventual ally to Zetta. He frist appears in Chapter 2, for the sole purpose of supposedly destroying Zetta. He then appears Zetta in other chapters for the same reason, often using his right-hand Raiden as a distraction. He then appears in Chapter 8, challenging Zetta to a final battle, until Salome interrupts. He appears in the final chapter, saving Zetta by contfronting Seedle. He finally appears in the Good ending, confronting Seedle once more, presumably killing him, then finally checking up on Zetta along with Salome and Pram after the game's credits. In some of the game's alternate endings, he manages to actually kill Zetta, saddened by the loss of his rival after conquering the universe.
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Alex is brash, arrogant, and persistent. He is also childish, furious when things do not go his way. He may consider Zetta a friend, since he saves his life twice, and then check sup on him in the Good ending. He most likely considers Zetta his friend and rival (Similar to Sonic and Knuckles, or Sonic and Shadow of the Sonic the Hedgehog series) but hides it behind fake death threats and wars. (214 Wars and over 60,000 assassins according to Zetta.) They both being Overlords, this is everyday life for them.
His Mana Aura is none other than electricity. It's timing and intensity depending on the level of his anger. Ironically, the thunder he uses to attack with is a green-ish color, unlike thunder is real life, which can be interpreted as yellow.
Alexander is by far the game's most unbalanced character. His signature weapon is the Drum, which is an INT-based weapon. However, his INT Aptitude is only at 100%, so he does not gain a major INTpower boost from his Drumssets. His real specialty is his 120% Aptitude in ATK, his 140% in HP, and 110% in TEC, making him a good physical attacker. He also gains 140% and 120% in DEF and RES respectively, making a possible tank and meatshield. He is good with Spears, Nunchucks, Drums, and Fans. His special, "Vanishing Bolt", is an INT-based attack, so if you choose to make him a physical attacker, he will never be able to use this skill effectively.
You can recruit Alex into your party (He will appear upon the start of the new cycle, as soon as you gain control) by defeating both him and Salome in the final map of Chapter 8, then beating him in the preceding Special Stage. Note that if Salome defeats Alex, or if Zetta defeats Alex first, the story will proceed as normal, forcing a reset if you wish to recruit Alex. Also, if you lose the Special Stage Battle, a unique scene will play out, then the Game Over screen will appear.
Alex is one of only two recruitable characters that you do not have to wish for in order to fight and recruit, the other being Pram the Oracle. Alex also appears in Disgaea 2 and it's PSP Port as a small fanservice cameo on Plenair and Usagi's news show.