An Action-RPG series by Square Enix known as Mana in the US, which involves Mana being the lifeforce of the world, and the Mana Goddess, Mana Tree, and Sword of Mana as central figures in each storyline. Seiken Densetsu literally translates to "Holy Sword Legend," or Legend of the Holy Sword.
The series is as follows:
Final Fantasy Adventure--Seiken Densetsu (GB, 1991)
Secret of Mana--Seiken Densetsu 2 (SNES, 1993)
Seiken Densetsu 3 (Japan Only, SNES, 1995)
Legend of Mana--Seiken Densetsu: Legend of Mana (PS1, 2000)
Sword of Mana--Shin'yaku Seiken Densetsu (GBA, 2003)
World of Mana Compilation:
Children of Mana--Seiken Densetsu DS: Children of Mana (NDS, 2006)
Dawn of Mana--Seiken Densetsu 4 (PS2, TBA)
Seiken Densetsu: Final Fantasy Adventure (Mobile, 2006)
Seiken Densetsu owns Kingdom Hearts!