Aratama and Nikitama (荒魂・和魂)
Aratama' (also referred to as 'Aramitama') and 'Niki(gi)tama' (also referred to as 'Niki(gi)mitama') are concepts used by Shinto to express two different aspects of spirits and souls of gods.
Aratama refers to the vicious aspect of gods, namely savage souls. It represents the intention by gods to cause catastrophic natural disasters, invite outbreaks of plague, and drive humans to conflicts and wars by wrecking havoc on their minds. The curses of gods are indications of Aratama. On the contrary, Nikitama refers to the gentle and tranquil aspect of gods, represented by blessings of nature such as rains and sunlight. God's blessing is an indication of Nikitama.
Aratama and Nikitama showcase strong (and different) dispositions of the same god so as to trick people into assuming that they are two different gods, when in reality, there are cases in which different names are given to the same god, or where the god's two natures are enshrined separately, such as Shogu and Aramatsurinomiya in Kotai-jingu Shrine. People have presented gifts to gods as tributes and performed ceremonies and festivals to mollify gods and transform them from Aratama to Nikitama. This extreme duality of gods' souls serves as a source of the Shinto faith.
Also, thanks to its vigorous quality, Aratama is said to contain energy that can create new phenomena and objects that can be linked with its homonym 'Aratama' (also referred to as 'Aramitama') meaning 'new spirits.'
Nikitama is subdivided into 'Sakitama,' (also referred to as 'Saki(chi)mitama') and 'Kushitama' (also referred to as 'Kushimitama'). It is said that the four (Aratama, Nikitama, Sakitama, and Kushitama) are parallel concepts. Sakitama presents bliss to people through luck, namely a good harvest. Kushitama present bliss directly to people through miracles.
Sakitama and Kushitama are represented by the word '豊' (rich) and '櫛' (comb), respectively, and these words are used for the names of gods or shrines
If we take a modern view, Sakitama and Kushitama can be interpreted as a private soul and a public soul, respectively. It is possible to understand that Sakitama and Kushitama equate to 'Betsutama and Kamitama' (a branch shrine for a deity and a memento).
Also, there is a belief that human's spirits consist of 'Naohi,' one spirit that is connected with heaven, and four souls (Aratama, Nikitama, Sakitama, and Kushitama); this concept is called "Ichirei shikon" (one spirit, four souls).
Incidentally, the word "殯宮" (funeral parlor) is pronounced 'Arakinomiya' in Japanese, and the first part of this word (i.e. "ara") is believed to have been derived from the word Aratama.