Spirits are entities born completely from Mana, thus making them superior to humans in raw power. However, they are akin to toy soldiers for the humans to toss at each other, leaving humans with a societal superiority over them. They are called "fairies" by Dragons and Eternity Swords.
They are born from the Sword of Rebirth with their Eternity Sword alongside them. When a Spirit dies, their bodily form vanishes in a golden light. Said golden light is their mana as it returns to the Sword of Rebirth.
They are divided into several types, which are visually, and easily, distinct. Most of the time, Spirits have a hair color and eye color dedicated to their Spirit type. Red Spirits have red eyes and hair, the same to Blue Spirits, etc.
These Spirits have the strongest attack skills, a mediocre defense, and the ability to use "Ice Banisher," which interrupts the activation of certain spells. Most of these spells that Ice Banisher cannot interrupt are generally Black Spirit spells or non-Spirit spells.
Bolstering the strongest defensive measure of all the Spirits, these Spirits are mostly attuned to nature. As a result, they are capable of Support skills oriented towards defending (healing, resurrecting, etc) their allies. They have an average-to-high attack power as well. Their main downfall is that they have a horrible Resistance in comparison to other Spirits, leaving them easily taken out by Red Spirit spells.
Fiery in both attitude and nature, Red Spirits excel in offensive support skills. Their ability to heat up an area's Mana and use it to burn their enemies to a crisp makes them exist solely to be offensive supporters, if they can get past Blue Spirit's "Ice Banisher." when used properly, Red Spirits will be a valuable asset to dismantling an entire group of Spirits by sitting in the back-lines. However, their defensive skills are rather pathetic, leaving them to be best at dishing out pain, but horrible at taking it.
Black Spirits are, stat-wise, the balanced Spirit of choice in all fields of offense, defense, and support. A saving grace of this Spirit is that they can attack multiple times within one combat interval -- they effectively wear down the opponent with quicker attacks that their foe cannot hope to counter. Defensive skills for Black Spirits are generally on the same tier as Blue Spirits, however their added bonus is that they deal a portion of their damage taken back to the attacker. Their Support skills are focused mostly on lowering the stats of the enemy group, either by specifically weakening their attack unit or by directly dealing damage to the enemy support unit. The most noteworthy trait of the Black Spirits is that all of their Support skills are "anti-Blue skills," meaning that, no matter what level of "Ice Banisher" is used, it will always activate.
White Spirits are extremely uncommon, so uncommon that the few of them that are known of in Phantasmagoria are Io Whitespirit and another Spirit by the name of Io. Io Whitespirit is extremely valuable in the sense of support magic, such as freezing objects solid or by purifying entire bodies of water. Effectively, the only White Spirit used in Eien no Astelia is usable only off the battlefield in every manner possible, whereas the Io that is fought in-campaign is meant specifically for combat.