Guide
How the kit works
Start with Night's Sling. Its Spirit Orb deals Nightsoul-aligned Electro damage and can bounce between nearby opponents. Each opponent can be selected only once per use; the Orb disappears after three bounces or when it has no eligible target left. Use Dark Voices Echo when available: it deals AoE Electro damage and creates a Supersonic Oculus that taunts opponents and fires Electro waves.
After the Skill, switch to another character. For 15 seconds, other party members' Hydro or Electro attacks that hit grant Ororon 5 Nightsoul points, up to 10 times. A nearby Nightsoul Burst also gives him 40 points, and he can hold up to 80.
With Nightshade Synesthesia unlocked, eligible reaction damage or another character's Nightsoul-aligned damage consumes 10 points to trigger Hypersense. It deals Electro damage equal to 160% of Ororon's ATK to up to four nearby opponents, once every 1.8 seconds. This also puts him in Nightsoul's Blessing for 6 seconds.
When the Orb hits, Aspect Catalyst grants Aspect Sigil for 15 seconds. The active character's Normal, Charged or Plunging Attacks can restore 3 Energy to them, and to Ororon if he is off-field. This can happen once per second, up to three times per duration.
Spiritvessel Snapshot (NA) has three Normal Attack shots and a fully charged Electro Aimed Shot. You do not need to stay on Ororon to use these in his usual off-field rotation.
Build and why
Use four pieces of Scroll of the Hero of Cinder City. When Ororon triggers an Electro-related reaction, it gives the party a 12% Elemental DMG Bonus for the elements involved for 15 seconds. If he is in Nightsoul's Blessing when he triggers it, the set adds 28% for 20 seconds. It works off-field, but bonuses from copies of the same set do not stack.
Noblesse Oblige is an alternative: four pieces give the party 20% ATK for 12 seconds after his Burst. Golden Troupe is an option for more Elemental Skill damage, though it does not describe a bonus to his passive Hypersense. For a mixed build, two pieces of Thundering Fury and two of Gladiator's Finale give Electro DMG Bonus and ATK.
Choose Energy Recharge or ATK Percentage on the sands, Electro DMG Bonus or ATK Percentage on the goblet, and CRIT Rate or CRIT DMG on the circlet. In substats, look for Energy Recharge first, followed by CRIT Rate, CRIT DMG, ATK Percentage and Elemental Mastery.
Elegy for the End is the first weapon choice. Its Skill and Burst hits build Sigils even off-field, and it gives Elemental Mastery. Polar Star boosts Skill and Burst damage and gives ATK stacks from different attack types. Aqua Simulacra increases the wielder's damage when opponents are nearby, even off-field.
For a 4-star option, Favonius Warbow can generate Elemental Particles on CRIT Hits. Alley Hunter increases damage while its wielder stays off-field; Rainbow Serpent's Rain Bow grants ATK after an off-field hit.
Leveling priority
A sensible talent order is Dark Voices Echo, then Night's Sling, then Spiritvessel Snapshot (NA). The Burst keeps dealing damage through its Oculus, while the Skill is used on each setup. Normal Attacks are less important if you switch Ororon out. Hypersense belongs to his passive, not either leveled talent.
For maximum ascension, gather 420,000 Mora, 168 Glowing Hornshroom, 46 Mark of the Binding Blessing, 18 Juvenile Fang, 30 Seasoned Fang and 36 Tyrant's Fang. You also need 1 Vajrada Amethyst Sliver, 9 Vajrada Amethyst Fragment, 9 Vajrada Amethyst Chunk and 6 Vajrada Amethyst Gemstone.
To maximize all three talents, the listed cost is 4,957,500 Mora, 3 Crown of Insight, 9 Teachings of Kindling, 63 Guide to Kindling, 114 Philosophies of Kindling, 18 Juvenile Fang, 66 Seasoned Fang, 93 Tyrant's Fang and 18 Lightless Silk String.
Constellations worth it
King Bee of the Hidden Honeyed Wine is a major personal damage upgrade. After the Burst, Ororon gains 8% Electro DMG Bonus for 9 seconds; additional opponents hit by the Burst or Oculus give another 8% each, up to 32% from those additional hits.
Ode to Deep Springs adds team support: triggering Hypersense gives the active character 10% ATK for 9 seconds, stacking up to three times. The Burst also triggers an effect equivalent to Hypersense at 200% of its original damage.
Trails Amidst the Forest Fog is worth considering for Hypersense damage. The Skill's Orb can bounce two more times and marks opponents for 12 seconds; marked opponents take 50% more damage from Hypersense.
As the Mysteries of the Night Wind gives Ororon 8 Energy after his Burst and makes the Oculus rotate 25% faster. If you are choosing where to stop, Roosting Bat's Spiritcage and A Gift For the Soul only add levels to the Burst and Skill respectively, so they are less compelling stopping points.
Teams
Ororon contributes off-field Electro damage and can restore Energy to the active character. With Scroll of the Hero of Cinder City, he can also give the party an Elemental DMG Bonus for the elements in his reactions.
Common mistakes
Do not expect Hypersense to fire without its conditions. Ororon needs at least 10 Nightsoul points and an eligible damage trigger; his Skill alone is not a substitute for the party's follow-up hits.
Do not leave him on the field using bow shots by habit if the team is built around his passive. Switch to the teammate whose Hydro or Electro hits can generate points, then use eligible reaction or Nightsoul-aligned damage to spend them.
Do not ignore Energy Recharge when choosing artifacts. His Burst deals damage and creates the Oculus, so being able to use it matters. Also check whether another teammate already carries Scroll of the Hero of Cinder City before doubling up: the set's damage bonuses do not stack.
Do not expect Aspect Sigil to restore Energy indefinitely. It lasts 15 seconds, needs an eligible attack hit and can restore Energy only three times per duration.