Guide
How the kit works
Use Dawnbearing Songbird to send Aedon at an enemy for Geo DMG. Tap it to send the bird forward, or hold it to aim at an opponent. Either the Skill or the Burst grants other nearby party members Lightkeeper's Oath for 20 seconds: their Geo DMG gains 5% CRIT Rate and 10% CRIT DMG. At Moonsign: Ascendant Gleam, they also gain 50 Elemental Mastery.
Cast Shadowless Reflection before switching to the character who will deal Geo DMG. It deals AoE Geo DMG and starts a 20-second effect with 21 stacks of Nightingale's Song. When a nearby active party member deals Geo DMG with an attack, Skill or Burst, a stack is consumed to increase that damage based on Illuga's Elemental Mastery. Lunar-Crystallize damage gets a further increase.
Hitting several opponents can consume several stacks at once. The effect ends when its time runs out or all stacks are spent. Geo Constructs on the field when Illuga casts his Burst, or created while the effect is active, grant 5 stacks per construct, up to 15 extra stacks within 20 seconds of the cast.
A passive increases the damage bonus according to the number of Hydro or Geo characters in the party, with thresholds of one, two and three. Oathkeeper's Spear (NA) provides up to four Normal Attack strikes; its Charged Attack consumes Stamina and lunges forward. Neither is the focus of this support setup.
Build and why
Use four pieces of Silken Moon's Serenade. Its two-piece effect gives 20% Energy Recharge. After Illuga deals Elemental DMG, the four-piece effect grants the party 60 Elemental Mastery at Nascent Gleam or 120 at Ascendant Gleam for 8 seconds. It also increases party Lunar Reaction DMG by 10% for each different Gleaming Moon effect present. Effects from Gleaming Moon cannot stack.
Four pieces of Instructor are an alternative: after Illuga triggers an Elemental Reaction, the set gives the party 120 Elemental Mastery for 8 seconds. Gilded Dreams is another option for Illuga's own Elemental Mastery; its four-piece effect depends on the elements of his teammates after he triggers a reaction.
For the sands, choose Energy Recharge or Elemental Mastery. Use Elemental Mastery on the goblet and circlet. In substats, prioritize Elemental Mastery, then Energy Recharge, then DEF Percentage. If the Burst is difficult to use consistently, an Energy Recharge sands is a practical choice.
Favonius Lance is the first weapon to consider. Its listed effect gives CRIT Hits a 60% chance to generate particles that restore 6 Energy to a character, once every 12 seconds. It needs CRIT Hits to work, so consider some CRIT Rate if you use it.
Dragon's Bane is another option; its listed effect increases damage against opponents affected by Hydro or Pyro by 20%. Kitain Cross Spear is an alternative for energy: after its Skill hits, Illuga loses 3 Energy, then regenerates 3 every 2 seconds for 6 seconds.
Leveling priority
For a support build, level Shadowless Reflection first: it supplies the stack-based damage increase that defines Illuga's role. Dawnbearing Songbird is a reasonable second choice for its Geo damage. Leave Oathkeeper's Spear (NA) until last if you rarely attack with Illuga.
For maximum ascension, gather 420,000 Mora, 168 Pine Amber, 1 Prithiva Topaz Sliver, 9 Prithiva Topaz Fragment, 9 Prithiva Topaz Chunk, 6 Prithiva Topaz Gemstone and 46 Cyclic Military Kuuvahki Core. You also need 18 Broken Drive Shaft, 30 Reinforced Drive Shaft and 36 Precision Drive Shaft.
To take all three talents to maximum, gather 4,957,500 Mora, 3 Crown of Insight, 9 Teachings of Elysium, 63 Guide to Elysium, 114 Philosophies of Elysium and 18 Eroded Horn. The talents also need 18 Broken Drive Shaft, 66 Reinforced Drive Shaft and 93 Precision Drive Shaft.
Constellations worth it
Nightmare Orioles is the standout upgrade. It strengthens Lightkeeper's Oath so affected teammates gain 10% CRIT Rate and 30% CRIT DMG for Geo DMG. At Ascendant Gleam, their Elemental Mastery increase becomes 80. You must have unlocked the passive talent first.
Elk With Fanged Antlers is worth considering for extra damage. While the Burst effect is active, every seven stacks consumed summon Aedon to hit one nearby opponent. The hit counts as Burst damage and scales with 400% of Illuga's Elemental Mastery and 200% of his DEF.
Earthshaking Maw adds three levels to the Burst, making it another useful upgrade for the support effect. Vigilant Sentinel can help with energy: after Illuga triggers a Geo-related reaction on the field, he recovers 12 Energy, at most once every 15 seconds.
Solarhunting Wolf gives nearby active party members 200 DEF while the Burst effect is active. Hurricane Steed adds three Skill levels. You can leave these as lower priorities if your focus is the Burst's damage support rather than DEF or Illuga's Skill damage.
Common mistakes
Don't leave Illuga's Burst until after your Geo damage dealer has finished attacking. Set up the Burst and its stacks first, then switch. Watch the stack count against groups: a hit on multiple opponents can spend multiple stacks, ending the effect before its 20 seconds are up.
Don't build only for Illuga's personal damage and overlook Elemental Mastery. It determines the Burst's damage increase. At the same time, don't ignore Energy Recharge if the Burst is often unavailable.
Don't expect Favonius Lance to generate particles without CRIT Hits, or assume its effect triggers on every hit. Finally, remember that the Skill and Burst's Geo CRIT buff applies to other nearby party members, not Illuga himself.
