"'Tis a spell worthy of the Necromancer himself. This allows me to dissect a creature's soul from its vessel of flesh. For these poor wretches, only oblivion awaits."
Spirit Death was a spell acquired and used by Kain during the events of Blood Omen: Legacy of Kain. It was found by him inside Dark Eden. This spell is one of the most powerful and expensive of Kain's repertoire, allowing him to throw a straight travelling projectile able to displace the victim's Soul from his body, causing an instant death. Though lethal, only a few of Kain's late enemies (especially the red Demons of Avernus) could survive a direct impact from this spell, demanding more than a single cast in order to die. Also, bosses were unaffected by this spell.
Like many of Kain's Blood Omen spells, Spirit Death is not seen in further games.
The spell is described in the 'Silicon Knights Blood Omen 1 FAQ' as an upgraded version of Energy Bolt (both being straight travelling projectiles), although Spirit Death uses more magic to cast (but causing a certain death), and could not be used to trigger wall switches (probably the most useful aspect of Energy Bolt).
The Spirit Death Incantation also features Blood Omen's take on souls, more readily featured throughout thelategames of the series (where they are depicted from green spheres to a glowing body outline). Spirit Death depicts an extracted soul as a semi-transparent outline of the enemy.