The tomes are four books with very high amounts of magic. Although a disprovable claim, these four books proclaim themselves to be guardians of dimensional magic that, according to them, goes beyond the power of normal gods. It is unclear who or what made them, but it is generally assumed that they've existed for a very long time, most likely tens of millions of years.
They usually remain in a dormant state, but once in a while, they will be awakened by those who find them. When this happens, every other tome will feel it, and usually, when one book is found, the magic of the tomes subconsciously causes the others to be awakened in quick succession.
A strange tome found by Amioun pilot Valexia Uskal. The tome has a will of it's own, and it's main purpose is to record the history of the universe. While it takes it's work rather seriously, it doesn't see anything wrong with purposely guiding history down a path it finds more interesting, which usually tends to lead to war and destruction. In fact, this directly led to the Apocalyptic War's disastrous results.
After the space-time distortion Epoch was later found by the Squin and was bound to Squaven.
The tome grants powers of time manipulation to those who survive it's power, and those who do not are possessed or destroyed. The aforementioned powers are limited in that they cannot permit one to make major and/or extensive changes to the past, nor can any of that be done any further than roughly a century into the past, and they cannot permit one to see and/or make definite things in the future any further than roughly a century. Any attempt to do such things would kill the user.
The tome of Ambit is a sapient spell-book from the same series as Epoch. However, rather than time manipulation, it grants it's user the power to control dimensional space. This includes shifting objects to other dimensional spaces, creating pocket dimensions and creating rifts which function similarly to a two point portal. However, like Epoch, mortal users are only capable of doing so much with the tome without suffering fatal side-effects, and the price for the power comes at a heavy risk, as you may be possessed or killed.
The Tome of Ambit was discovered by the pilot of Unit Paladin.
Anima is the Tome of Souls, and is able to control the souls of the dead to either resurrect, alter or reincarnate them. It grants it's user the powers over souls. Anima's main use to it's user is it's ability to create absolutely loyal armies and the fact it can resurrect the dead foes of it's master to snowball their own army further. The limit of the usable power for mortals remains a factor even for Anima, as using his powers too heavily can put considerable strain on it's master.
While Anima has a rotten, all business attitude he is still obedient to those who are able to read him. No matter how much he may complain.