Vajrasattva (rDo-rje sems-dpa’) practice is a tantric meditation done for the purification of karma. As a Mahayana practice, it is undertaken with a bodhichitta aim to purify all our karma in order to reach enlightenment as quickly as possible in order to be best able to help all limited beings (sentient beings). On an ultimate level, Vajrasattva practice is non-conceptual meditation on voidness (emptiness). On a provisional level, it entails repeated recitation of a hundred-syllable mantra (yig-rgya), accompanied by opponent states of mind and complex visualizations.
Vajrasattva mantra recitation and visualization may be undertaken merely within the context of sutra practice, before beginning any practice of tantra. In such cases, it may be done either with or without being part of a set of formal “preliminary practices” (sngon-‘gro; “ngondro”) for tantra, during which we would repeat the mantra 100,000 times. The recitation and visualization may also constitute part of a formal tantric “sadhana” (sgrub-thabs) practice for actualizing ourselves as a Buddha-figure (yi-dam). Such sadhana practice may be within the context of any class of tantra.
Regardless of which level on which we practice Vajrasattva meditation, it is aimed at purifying ourselves of karma. Karma (las) refers either to the uncontrollably recurring mental urges that bring us to act, speak, or think in a specific manner, or to the impulses with which those so-called “karmic actions” are carried out.