Feeding the Reaver

Feeding The Reaver is an ability that both the Wraith Blade Reaver and the Soul Reaver can manifest and use.

Wraith Blade
This ability is first seen with Raziel in Legacy of Kain: Soul Reaver 2 where in the Sarafan Stronghold he encountered William the Just tomb along with his incarnation of the Soul Reaver (broken, by Kain). Raziel wipes his claw that his symbiotic weapon is attached to, a reaction occurs and Raziel grasps the physical reaver, and both reavers drain Raziel of his Health and health augments from Soul Reaver 1. Raziel's manifestation of this in Soul Reaver 2 is a ring the encirlces his Soul Spiral and lengthens while the wraith blade gets stronger, however if it fully encircles Raziel's health coil, it will begin to feed off him. In Defiance, the meter has changed to be a reaver-shaped bar that will fill up as Raziel strikes and takes the souls of enemies with the wraith blade and when fully charged will be able to cast a 'Reaver Spell' along with the secondary effect of doing an automatic attack.

The physical Reaver
Although present, this meter doesn't become usable until Kain finds the Balance Emblem and performs similarly to it's wraith blade counterpart (with the substitution of blood as opposed to souls). It will also perform spells and secondary automatic attacks when fully charged as well.

Trivia

 * Although Constrict is not present in Soul Reaver 2 and Defiance for gameplay reasons, fans have attempted to reconcile this; arguing this is because of his meetings with Moebius' Staff and the physical Reaver blade in the Sarafan Stronghold, with the constrict ability now working as the coil around Raziel's health bar when the Wraith blade is aroused. One reason why is because of encountering Moebius' Staff which affects vampires and affected Raziel's constrict ability because it is vampiric energy mixed with spiritual energy (which is the initial reason why it is not seen), the second reason is because of the broken soul reaver that belonged to William the Just (the reavers stole these energies that composed the constrict ability from Raziel and mutated them into this ability represented by a ring in Soul Reaver 2 and a reaver-shaped meter in Defiance for Raziel).


 * It is believed by fans that for Kain's (Blood) Reaver that this meter couldn't be used because he didn't have the Balance Emblem, because on its own the (Blood) Reaver was designed to steal blood from its victims but the Balance Emblem and its fragments give the (Blood) Reaver new abilities and spells that require blood (as a fuel) and the meter is just a representation of how much blood (or fuel) has been absorbed and how much is need to be able to cast a Reaver spell.