Correction, September 11, 2026. This guide was published from pre-release impressions and got Rhiannon's fundamentals wrong. It described her as a Reality-damage burst carry who wants a Crit-first Resonance grid, and it said she was weak to Star. All three are wrong. Her damage is Mental, her own Insight text calls her an All-Rounder, and Beast loses to Mineral, not Star. The guide below has been rebuilt against her live kit. If you invested in her as a Crit carry on our advice, the section on stat priorities explains what to do instead.
Rhiannon was the face on the anniversary banner, and the trailer sold her the way trailers sell everyone: big bird, big numbers. What she actually does is quieter and, for most accounts, more useful. She holds the squad's damage buff and the enemy's crit-defense shred at the same time, then occasionally hits the whole screen for a great deal of Mental damage.
She is a 6-star Beast Arcanist dealing Mental damage, the Phase 1 headliner of Version 3.7 "On Another's Sorrow", and the wiki's role tags read Support and All-Rounder. Build her that way.
The engine: Attunement in, everything else out
Every card Rhiannon plays is paid for twice. The card does its printed job, and before it resolves it eats a stack of Attunement to give her something extra. She starts each round with 2 Attunement, so you get two paid cards a round and the third is a plain one. Merging matters here in a way it does not for most supports: a merged card still spends only one Attunement, so merging Babble-Gabble to level 3 gets you 500% instead of 200% for the same stack.
| Card | What it does | What the Attunement buys |
|---|---|---|
| Babble-Gabble | Mass attack, 200% / 300% / 500% Mental DMG by merge level | ATK +12% to +14% for 3 rounds |
| Sneaky-Peeky | Mass buff, grants Flocksong to all allies for 3 rounds | Max HP +12% to +14% for 3 rounds |
| Chirping Chorus (Ultimate) | Grants Adar Llwch Gwin to all other allies for 3 rounds, and puts Rhiannon into Bendith for 4 rounds | Nothing, it is the state change |
At Insight 3 the leftover Attunement stops going to waste: at the end of the round she converts one spare stack into Moxie +1, and she starts the battle with Moxie +3 and 70% of her Raptor Kinship gauge already charged. That is the single biggest reason to push her to I3 rather than parking her at I2, and it is the opposite of the advice this page used to give. If materials are the bottleneck after the anniversary, the currency and farming guide covers where to spend Sharpodonty first, and the investment order explains why I3 outranks a fourth half-built unit.
Bendith is the whole point
Chirping Chorus is not a damage button. It flips her two ordinary cards into their reinforced versions for four rounds, and the reinforced versions are where her value lives.
- Babble-Gabble · Bendith hits for 400% / 600% / 1000% Mental DMG to all enemies and then applies Critical DEF -15% to everything on the field for 3 rounds, plus a further -3% per stack of Rapport she holds, capped at another -15%. Fully stacked, that is a 30% crit-defense shred on the whole enemy line.
- Sneaky-Peeky · Bendith keeps the Flocksong buff and adds DMG Bonus +15% to the entire squad for 3 rounds, again plus 3% per Rapport stack up to another 15%. Fully stacked, +30% team DMG Bonus.
Two AoE effects, both team-wide, both scaling off the same resource. A carry standing next to a stacked Rhiannon is hitting harder and into softer crit defense at once. That stacks multiplicatively with what your actual damage dealer brings, which is why she improves a good team more than she improves her own damage number.
Her fourth card, Feast Call, is the exception: a mass attack for 1500% Mental DMG plus 150% per Rapport stack, and it always counts as a Stronger Afflatus hit regardless of what you are pointed at. That last clause matters more than the multiplier. It means her one big swing ignores the type wheel entirely.
Stat priorities, and what to undo
If you followed the old version of this page and dumped Resonance into Crit, you did not brick her, but you did buy the wrong thing. Her max-level crit rate is 14% and her crit damage is 21%. She is not a crit unit and no grid will make her one.
What her kit actually converts:
- ATK. Feast Call scales off it, Babble-Gabble scales off it, and her Attunement spend is itself an ATK buff. At Portray 4 her Adar Llwch Gwin buff hands allies ATK equal to 10% of hers, so on a whaled account ATK is doing double duty.
- Mental DMG Bonus, since every offensive line in her kit is Mental. The old advice said Reality. Reality does nothing for her.
- Max HP and survivability nodes are genuinely fine here, which is unusual advice for a 6-star. Her Sneaky-Peeky Attunement spend is a Max HP buff, and she needs to be alive and casting for her buffs to persist. Take the defensive nodes on the way to the offensive ones and do not feel clever about skipping them.
Skill levels: Sneaky-Peeky and Babble-Gabble before Chirping Chorus. The Ultimate's effect does not scale with level in any way you will feel; the two cards it reinforces do. This is also the reverse of what this page previously said.
Psychube: what she wants, and what we will not claim
Her psychube should push ATK and buff uptime, not single-target burst.
We are not going to name a best-in-slot. We could not verify a signature or community-consensus psychube for her from a primary source, and inventing one is how this guide went wrong the first time. Treat the specific psychube as unconfirmed. The stat profile is not: slot the highest-ATK support-oriented psychube you own, max its Resonance, and ignore anything whose text keys off single-target damage or Ultimate damage.
The rule that survives regardless: a fully upgraded common psychube beats a bare premium one, every time.
Where the Beast tag actually hurts
Rhiannon is Beast, so she is advantaged into Plant and disadvantaged into Mineral. She is neutral against Star, Spirit and Intellect, because those three form their own separate triangle that never touches hers. Our Afflatus guide has the full wheel.
In practice the tag costs her less than it costs a carry. Buffs and debuffs are not reduced by afflatus disadvantage, so a Mineral-heavy stage does not switch her off, it just makes her own chip damage worse. And Feast Call is written to always land as a Stronger Afflatus hit, which papers over the rest. She is closer to an all-content support than her Beast icon suggests, which is exactly why the roster tags her All-Rounder.
Teams that use what she gives
Build around the fact that her output is a squad-wide damage buff and a squad-wide crit-defense shred.
The obvious one: put her behind a crit carry. Critical DEF -30% is worth the most to a unit that crits often and hard. A Reality or Mental carry with a real crit build gains more from her than a steady-damage unit does. Pair with a healer and a second buffer and you have the standard four-seat shell from our team building guide.
The AoE clear team. Both of her attack cards are mass attacks, so on wave content she is contributing real damage while buffing. Slot her with another AoE unit and a sustain seat and stages that would take three rounds take two.
The budget version. Rhiannon plus free and low-rarity supports plus any 4-star or 5-star healer clears current content, because a +30% team DMG Bonus does not care how expensive the units receiving it were. This is the comp to run if the anniversary emptied your Clear Drops.
For where these land against the rest of the patch, the 3.7 best teams tier list ranks the anniversary comps head to head, and the banner schedule tracks what is live now.
Portrays: P2 is the real breakpoint
Most guides say P0 and stop. For Rhiannon that advice needs one asterisk, because her Rapport ceiling is gated behind dupes and Rapport is what powers both of her Bendith effects.
- P0 is a complete, functional unit. Everything above works at zero dupes.
- P1 gives Moxie +5 on entering battle instead of +3, and upgrades Flocksong to Incantation Might +45% and Ultimate Might +45%.
- P2 is the meaningful one: Rapport stacks up to 7, each stack adds 5% Stronger Afflatus DMG Multiplier, and Feast Call jumps to 3000% plus 300% per stack. More Rapport means more of both Bendith effects.
- P5 pushes Rapport to 10 and Feast Call to 5000% plus 500% per stack. Whale territory.
Unless you are committed to her, P0 and spend the pulls on roster breadth. A second advantaged carry does more for your account than her P1. But if you free-pulled into P1 during the anniversary, P2 is a better use of spare currency than it would be on most supports.
Is she worth pulling?
If you evaluated her as a carry and passed, re-read the pitch. A unit that hands the whole squad +30% DMG Bonus while stripping 30% Critical DEF off the whole enemy line is not competing with your damage dealer, it is multiplying them, and supports age far better than carries in Reverse: 1999. If your bench is already deep in buffers, she is a comfortable skip, and Ms. Stranger in Phase 2 may fill a bigger hole.
Whatever you decide: check the tier list and the live banner schedule before you spend a Unilog, and build the unit you pull properly before chasing the next.
Kit details, multipliers, Insight effects and Portray values in this guide are transcribed from Rhiannon's entry on the Reverse: 1999 Wiki and re-checked September 11, 2026. Her base Rapport cap at P0 and a best-in-slot psychube remain unconfirmed and are flagged as such above.
