Legendary TechniqueOn the site the most powerful rank is not SSS-rank rather a select few have the opportunity to learn a Z-rank technique. Only specific characters can learn this technique and they must fill one of two requirements: the first is a completely maxed out Jutsu Limit not including those increased through Specialization Training. The second is a 2500 Word Solo Training that cannot be lowered by specs, gifts or anything that reduces the required word count for trainings, after which the character is made Elite and cannot rank up any further whether they change factions or anything of the like.
There is a third requirement and it is perhaps the most important. This is that
No Other Character from that Account can have a Z-rank. There is only 1 Z-rank technique per account and once that character dies, they are then allowed to learn it again with another character after fulfilling the requirements all over again.
Training for the Z-rank = Free once you have maxed your character or completed a 2500 Word Training.
*In regards to the specialization that allows for two characters to possess a Z-Rank, this applies only to the first time, the second requires a 2500 (if maxed) or 3000 (if trained) Word Training Topic, that cannot be reduced by any means, to learn it.
Shinobi/Kunoichi the Z-rank is available to:Elite Genin
Chunin Instructor
Elite T. Jonin
Elite Med-Nin
Elite Jonin
Hunter Nin Captain
Kage
Gokage
Koikage
Missing Nin the Z-rank is available to:Elite C-Rank
Elite B-Rank
Elite A-Rank
Elite S-Rank
Z-rank
X-rank
*Note it is possible to obtain 2 Z-ranks IF and only IF one of them is a Combination Technique. The second is required to be trained and must be comprised of 3 SSS-rank techniques. If this is done, similar to the one per account rule no other Character in the account can possess a Combination  Technique Z-rank, it likewise forfeits the account's ability to have a character learn a X-rank Combination Technique until one of said user's dies thus resulting in the inability to use it anymore due to one of the users being no longer available.
EquivalenceThe Z-rank is equivalent in damage to 3 SSS-ranks, due to that massive power difference they are often considered to be nigh unstoppable. Z-rank level damage is also impossible to reach with self combination jutsu when the power of a technique gets to that level it becomes volatile and detonates killing the user attempting it. This of course only applies to self combination jutsu rather than utilizing multiple SSS-ranks to counter a Z-rank technique.
In terms of cost Z-rank uses a unique system which is based on the rank of the user and uses their Entire system to calculate the drain it costs the user.
Hybrid uses which ever system comprises it however in the case of techniques not in the Hybrid category it takes from each system that it does damage. (e.g a Z-rank Technique which does Physical, Chakra & Spiritual damage from a Elite Jonin will consume half of their Fatigue, Chakra Reserve AND Blood Limit)
Rank Reference- Spoiler:
D-rank - Academy Student
C-rank [Low] - Genin
C-rank [High] - Missing-Nin
Elite C-rank - Elite Genin
B-rank [Low] - Chunin
B-rank [High] - Tokubetsu Jonin, Missning-Nin
Elite B-rank - Chunin Instructor, Elite Tokubetsu Jonin
A-rank [Low] - Jonin
A-rank [High] - Hunter-Nin, Med-Nin, Missning-Nin
Elite A-rank - Elite Med-Nin, Hunter-Nin Captain, Missing-Nin
S-rank [Low] - Combat Med-Nin, S-Class Hunter-Nin
S-rank [High] - Sannin, Missing-Nin
Elite S-rank - Head Nin, Hunter-Nin Commander, Kage
"Z"-rank - Gokage, Leader of S-rank Missing-Nin Org/Bounty
"X"-rank - Koikage, Leader of Z-rank Missing-nin Org/Bounty
Chakra uses the Chakra Reserve Limit
- Spoiler:
Elite D - Full
Elite C - Three-Fourths
Elite B - Two-Thirds
Elite A - Half
Elite S - One-Third
"Z" - Quarter
"X" - Eighth
Mental uses the Nen Limit and is only available if one has Nen
- Spoiler:
Elite D - Full
Elite C - Three-Fourths
Elite B - Two-Thirds
Elite A - Half
Elite S - One-Third
"Z" - Quarter
"X" - Eighth
Physical uses the Fatigue Limit
- Spoiler:
Elite D - Full
Elite C - Three-Fourths
Elite B - Two-Thirds
Elite A - Half
Elite S - One-Third
"Z" - Quarter
"X" - Eighth
Spiritual uses the Blood Reserve Limit and is only available to those who have Blood
- Spoiler:
Elite D - Full
Elite C - Three-Fourths
Elite B - Two-Thirds
Elite A - Half
Elite S - One-Third
"Z" - Quarter
"X" - Eighth
Natural uses the Natural Energy Reserves and is only available to those who are able to harness Natural Energy
- Spoiler:
Elite D - Full
Elite C - Three-Fourths
Elite B - Two-Thirds
Elite A - Half
Elite S - One-Third
"Z" - Quarter
"X" - Eighth
*Note: If the user of this technique does not have the required amount to sustain this technique even if it is just 1 D-rank off they instantly die upon preforming the technique. In addition if they use up their entire limit to preform this technique the next technique they will succumb to the effects of Chronic Fatigue, Blood Loss, will die from chakra exhaustion with an additional technique use, will be knocked unconscious from over Nen use, will be knocked out of Sage mode, Petrify from overusing Natural Energy.
Legendary Combination JutsuWhile the most powerful rank is in fact a Z-rank, Combination jutsu likewise have a threshold max which goes by a final Ranking system after which any additional strength will result in an unstable combination detonating and killing all the participants involved. Unlike the Z-rank the X-rank Combination Art is not restricted per account but rather by character(s). Likewise just like all other Combination Jutsu the X-Rank Combination Art can only be formed if all members are present to form it.
EquivalenceThe X-rank is equivalent in damage to 9 Z-ranks, due to that massive power difference they are often considered to be Deity level power. X-rank level damage is also impossible to reach with self combination jutsu when the power of a technique gets to that level it becomes volative and detonates killing the user attempting it. This of course only applies to self combination jutsu rather than utilizing multiple SSS-ranks to counter a Z-rank technique.
Likewise any combination jutsu utilizing post Z-rank Damage can be considered "X-Rank" however it is vastly underpowered in comparsion to a true X-Rank. So far only the Bijuu have demonstrated the potential to utilize an X-rank Combination Art by each chaining their Z-rank Menancing Ball together. Other than the Dieties themselves, only the Juubi is capable of utilizing an X-rank on it's own.
Just like a Combination Art the cost of an X-rank stems from all the parties involved however all X-rank Combination Arts even those which are not true X-ranks consume a Z-rank price from each of the participants involved. Likewise just like Z-ranks if it is hybrid based it takes a Z-rank price from each of the energy sources (Fatigue,Chakra,Nen,Blood) that are involved in the combination. As a result X-ranks have some of the harshest costs of techniques on the site as a way to balance their power.