Spirits

From MTG Salvation Wiki

A spirit may be a sentient or non-sentient entity composed of energy related to a deceased or worshipped object or concept. Its origin may be related to the way the previous being was killed- as a vengeful spirit (as featured in Shadowmoor), as a form of undead (as seen in the Orzhov Syndicate), or as an aspect of life (as the kami of Kamigawa).