Necromancy is a form of magic that allows the user to manipulate anima, also known as life force or, more accurately, spirit energy.[1] In this sense, it is similar to Paladin magic, but it is also different, for a necromancer's magic is in most cases—with very limited exceptions—focused in a negative one.[1] Reversing necromancy entirely is something very few necromancers have the knowledge or ability to do, such as Zorbak and Diviara Celegra[1] (Frostval 2012: Gift Delivery!).
According to Falerin Ardendor*, necromancy tends toward Darkness above all other elements and is indeed the normal form. There are some odd exceptions to this, generally either very powerful necromancers, or very powerful mages who understand enough of the underlying principles of magic to mimic necromancy in other ways. Undead themselves however can definitely be multielemental even if the magic used to bring them back to life is Darkness.[1]
According to Alina*, the use of spirit orbs is involved.[1] The Brilhado, however, use a different sort of necromancy to that of Zorbak's, in that make extensive use of the Cold to do their magick. (Frostval 2012: Gift Delivery!)