Pretty solid analysis. The ability is very Lovecraftian by design. It's also why Sanity works as a double edged sword but the user always has the upper hand because of their innate resistance.
Very (very) brief synopsis: Yes, Tiamat was born from the Void and created the gods, her first children. Humans were made by the gods leading up to a massive war between the gods and Tiamat. Two years ago she was released through Imeroth's machinations. But her motives then are heavily suggested to be because of Abzu's machinations, something that is a recent revelation but also has been foreshadowed for the past year or so.
So here's the actual Doujutsu technique. Pretty simple stuff. Some parallels that can be drawn to Sharingan. In terms of power, I'd rank it stronger than Sharingan (hence the 8,000 Kumi value) but weaker than MS.
(Dōjutsu: Shinkaigan) – Eye Technique: Abyssal Eyes
Type: Supplementary
Rank: A
Range: Short – Long
Chakra: N/A (-10 per turn)
Damage: N/A
Description: The Shinkaigan (深海), or the Abyssal Eyes and the Eyes of the Abyss, is the Dōjutsu Kekkei Genkai that appears in the Voidseers. Two conditions must be met to awaken the Shinkaigan. The first is that one must become Void-touched; this is achieved when one becomes Void-touched. The second is by gaining sufficient knowledge of the Shinkaigan and the Voidseer’s innate abilities. This is a key characteristic of the Shinkaigan, noted by Solomon to be “eyes of knowledge” rather than “eyes of trauma,” making it distinct from the Sharingan. The Shinkaigan possesses a unique connection to the Void itself. Its abilities exist in both space and time separately. This comes to be because the Void exists both as a separate dimension and a state in time. Rewinding the clocks far enough would cause everything in the universe to eventually converge onto the Void. The Shinkaigan is the only way one can view the Void directly, peering into it to gain intimate knowledge of the inner workings of the universe as it is today. Without the Shinkaigan exposure to the Void and Shinkaigan Dōjutsu causes one to lose Sanity; though, like a double-edged sword, the Shinkaigan user also suffers a loss of Sanity. But because their eye allows them to perceive and cognize the Void differently from other humans, they lose Sanity at a slower rate. In the left eye the Shinkaigan allows the user to visually perceive lifeforce and lifecycles of anything, including inanimate objects. It derives this ocular power through the nature of the Void itself. The right eye allows the Shinkaigan wielder to view the Void as a physical space, perceiving it not as a point in time but a location. The wielder gains enhanced visual acuity, able to track targets at four times their speed. Though unlike other Dōjutsu it lacks the ability to perceive chakra. Activation of the Shinkaigan grants the user access to their Voidseer Dōjutsu, affording them the ability to use powerful temporal and spatial abilities.
Note: The user is able to passively activate the Shinkaigan after holding the Dōjutsu for one month.
Note: Gazing directly into the Shinkaigan causes a loss of 5 Sanity per turn unless the user also wields the Shinkaigan. Those who have completed Taijutsu training can avoid these effects by breaking eye contact with their opponent.
When choosing the bio I wanted the ability on I struggled with finding the right character for it. I went with Natsu as it’s a bio suited to me and specced fully into fire release as it’s the way I prefer to fight, so when I make use of the shinkaigan my own natural fighting style will regen my sanity on top of the natural resistance. Seemed to work out well.
So much like all doujutsu, after a month I can do it passively which is a good start.
The eyes act as a medium, the way in which you see the void. This is why people lose sanity in looking into your eyes. As you as the user have been using these eyes and trained for a month before the view the void, you have greater resistance to the loss of sanity. People will lose sanity if they make eye contact that is pretty cool as it plays well with the eyes being the medium for the control of the void. The eyes being used to speed up the life cycle of something to revert it back to the void or to summon the void itself as an energy. Chakra is used to summon the void but void energy is not chakra. The eyes increase your tracking by x4 but unlike other doujutsu, you cannot see chakra.
The left eye sees life cycles through it. I spoke to Nk about some stories to explore in the ninja world, is there any way to use this aspect to see the history in a land mark in a sense?
Where the left eye perceives the time aspect of the void, the right eye is connected to the space aspect. Through the right eye, you summon the energy from the void which will be limited to mid range for this level of Shinkaigan. The void energy is like a cross between fire and water in it's a appearance, though an energy with no temperature, it looks like a dark blue/purple energy.
This energy is chaos and with it comes with an aspect of randomness tied to it. The first is you use the roll based system to determine if the damage of the technique is randomly increased or not. The second is you role as the energy takes on the strengths and weaknesses of one of the basic 5 elements. This energy moves at the speed of lightning release techniques.
How do you go about upgrading the eyes to their fullest potential such as the cosmic shinkaigan? Is that through the NW only?
Where it says it moves at the speed of lightning techniques, is the speed defined by the rank of the technique? The chakra of the technique or the damage of the technique?
Example:
(Dōjutsu: Kirameku Fuka) – Eye Technique: Shimmering Depths
The technique is A rank, using 30 chakra, but can have up to an addition 40 damage increase based on the roll aspect. When choosing it's speed would it be A ranked lightning speed or F ranked lightning speed because of the damage increase? (I don't know if increasing the power of a technique increases it's speed with boosting)