Resurrection

Death, by its nature, is permanent. It takes more than a simple prayer and some diamond dust to undo a Death. There are few who regularly practice the arts of resurrection in Aedeva because the act of resurrection is incredibly dangerous, requiring the caster to journey through the River of Death itself to recover the victim's soul.
Note: learn more about the River of Death and traveling it to resurrect people at Traveling the River of Death.

Mechanics

Each of the resurrection spells is cast as normal, but instead of the written effect it transports the caster into the River of Death, where they must find their target and drag them back to the world of the living.
If a diamond is used and the spell would send the caster deeper into Death than the target is (for example, if the target's soul is in District 3 and the caster casts True Resurrection), then the caster is brought directly to the target.

Revivify

This spell starts the caster within the Border of Life on the banks of the River of Death.
The diamond used, if any, must be at least Tier 3.

Raise Dead

This spell starts the caster within District 3 of the River of Death. It can be upcast to level 6 to start in District 4.
The diamond used, if any, must be at least Tier 5.

Reincarnation

This spell does not send the caster into the River of Death. However, there is no telling what form the target may have on their return.
What is more, reincarnation requires a lengthy ritual, taking one day for every level the target possessed.
You cannot reincarnate a creature whose soul has traveled beyond District 5.
A diamond is required for Reincarnation, and must be at least Tier 5.

Resurrection

This spell starts the caster within District 5 of the River of Death. It can be upcast to level 8 to start in District 6.
The diamond used, if any, must be at least Tier 7.

True Resurrection

This spell starts the caster within District 7 of the River of Death. It cannot be upcast.
The diamond used, if any, must be at least Tier 9.

Wish

Unlike the others, this spell does not send the caster into the River of Death. Instead, it simply brings them back to life. Resurrection by this spell is less predictable than the traditional method though, and can have a myriad of... interesting side effects.
Additionally, you must provide a diamond that is at least Tier 9.

Resurrection Information

As long as you have a diamond you should be relatively safe. It is an offering that will serve as your lifeline back into the living world. It is not strictly necessary, but to enter the River of Death without one... Well, best not to do that.

— Master Qilnoi of the Sands

This magic is incredibly rare and is considered sketchy, or even illegal, in many societies because it is considered to go against the natural flow of life. Nonetheless, with the right contacts, one might find an old crone or outcast wizard willing to sell the knowledge for the right price. In such situations, resurrection spells are often marketed as a simple way to undo the untimely death of a loved one, but the truth is more complex.
On casting resurrection spells, the caster will find themselves thrust forward into the river of death itself. Only the soul can make this journey, and the body is left on the river's shores in the realm of the living, coated with a thin layer of frost that forms from the river's frigid cold. Completely helpless.
Once in the River, the caster must be wary of all of the realm's dangers, including (but by no means limited to) powerful undead who are eager to escape back into the world of the living; sudden sinkholes and whirlpools that can bring an unwary traveler suddenly deep within the river's current (a place from which there is little to no turning back the gates that separate the River's so-called "districts" with deadly power; or any number of other strange creatures and phenomena that haunt that strange place.
Once in the river, the caster must find their target, the dead creature on whom they cast the spell, take them, and drag them back out of the River's clutches. What is more, they must hurry, for the river is always pulling the target (and the caster) deeper into its cold embrace.
If the diamond is used in the spell's casting, then the extra offering provides guidance and protection. It allows the caster to easily locate their target and, once the target's soul is grasped, aids the caster's journey back upstream, steadying their feet and guiding them to the entrance back into the realm of the living. It also protects them from the river's soul-draining cold. Without the diamond, the caster gets no such benefits, and should they plunge into the water's frigid depths, they will find themselves joining their target on the long ride down the river's current.

Other Resurrection Spells

There are other spells that can allow the resurrection of dead loved ones or allies. These spells are more powerful than Revivify, but that power comes at a cost. Each one causes the caster to begin their journey from deeper within the river of Death. This gives a higher possibility of catching the target and dragging them home than if the caster must chase them downstream, but it also forces the caster to traverse much deeper into the river itself. A prospect that the wise caster will both respect, and fear.
In general, a resurrection spell causes you to start your journey at the district corresponding to the spell level at which the resurrection spell was cast. So if you cast Raise Dead at 5th level, then it sends you to the 5th district of the river. If you cast the 9th level Resurrection, you will be sent to the 9th (and final) district of the River of Death.