Name: Sage Mode
Rank: N/A
Range: Self
Elements: N/A
Specialties: Kuchiyose
Hand Seals: N/A
Description: https://naruto.fandom.com/wiki/Sage_Mode

Anyone can become a "sage" at any rank. Two full Sage are active at a time. Sage Mode does not count as a derived jutsu for advantages. Minato also dismissed learning Sage Mode, and in combining it with his bijuu Naruto didn't receive a substantial difference. 3 summons in the contract can use Sage Mode after becoming a Perfect Sage.

Natural Sage: An optional level. Taking this limited and doing 30k training allows learning one's 5th element naturally although they can't learn Sage Mode. All 5 elements are required for cursed seals like Orochimaru's Juinjutsu along with studying Jugo's clan.
Partial Sage Mode: 5k training.
Perfect Sage Mode: 10k training.

Natural Energy
Posts spent preparing Sage Mode is "turning" your pool into natural energy able to be used. Partial Sages can turn 50% of their pool into natural energy and can't sense. Partial Sages gather at a rate of 10% per post. Perfect Sages can use their whole pool for Senjutsu and can gather it at a rate of 20% per post. Clones do not copy Sage Mode state unless distributing the sage chakra.

Holding still can counter direct chakra absorbing and the opposition will suffer the fate that those in your contract suffer for failing to learn Sage Mode properly. Killing non-trained absorbers of natural energy is possible only if they absorb directly by physical contact and decide to add chakra to their pool. Jiraiya's jutsu was absorbed and Madara absorbed Rasenshuriken.

Stats
Partial and Perfect Sage Mode give chuunin stats if not above it. A databook has compared Lee to Naruto in a state beyond Sage Mode so it's not considered to be an all-encompassing buff here in comparison to Eight Gates. Chakra can reach Elder with jounin the base stat, but cursed seals do not get this benefit. When Sage Mode is combined with chakra mode it allows scaling to an opposing instinct stat. As will be the case with all cursed seals Sage Mode can only swap 2 stats to a higher level.

Senjutsu
Jutsu are better in all stats if at the same stats, similar to physical specialties, but for jutsu. This can only apply to one jutsu at a time with one function and is monitored for abuse.

Sage Mode sensing is inconsistent. The way it works here is that it primarily scales to what people in the topic are sensing through chakra. Meaning if entering Sage Mode randomly a user won't usually run across an entire village. If there are no sensory abilities in the topic then student chakra sensing is used for 100 meter range.

Group or Character Tied?: Yes limited
Requirements: Limited, jounin-level chakra. Learners need to be acquainted at one point with another PC member IC (such as Jiraiya) with the same summon contract, but neither users need to already know Sage Mode. Sage Mode is trained by learning from a NPC summon or a member with Sage Mode. Requires full kuchiyose specialty.
Deriving: Orochimaru's Juinjutsu and cursed seals are above.