Iyo

Iyo’s skills are split into two parts. Her first two skills are typical looping boosts, giving an Arts boost and a charge. Her second and third skill provide Critical boosts. Unfortunately, there is an overlap with her second skill, requiring Masters to prioritize Noble Phantasm or Critical Damage. Masters will usually pop the first and third skill turn 1, and save her second skill until turn 2 or 3, whenever she needs the damage boost.

• Kidou (Ruin) B primarily is used for Iyo’s Arts boost, giving her extra damage and refund for looping. In certain niche cases when facing a Divine enemy it will give her further damage, though in practice this is rare. This also gives her an on-demand curse, although this is almost never relevant. Masters want to use this immediately as a basic damage boost throughout the fight. As the Arts boost is necessary for looping, this should be leveled second and to max. 
• Oracle of Darkness B is a two-horned beast. On one horn it gives Iyo a 30% on-demand charge, giving her looping potential. On the other, it gives a 1-turn steroid to Arts Critical damage, boosting both Critical damage and gather rate. Masters will want to save this skill until later in the fight, preferably turn 3. It is all right to use Oberon’s skill 2 on her turn 2 as this 30% will more than make up for it. We want this turn 3 so that if her damage is not enough to clear the wave, she can use Critical damage to overcome the remainder. This is a scaling charge skill, so level it first and to max. 
• Priestess of the End C at first glance appears to be a rather weak skill with a niche application of Critical Damage to the rare Wild Beast Ally, a small pool of Critical Stars, and a weak Charisma for the party. But as Iyo has a passive which gives her the Wild Beast trait, this means that it is a 50% Critical Damage boost for her for three turns. Masters want to pop this on her first turn to take full advantage of this. It can be leveled last and left at level 6 if Masters want to save materials, but is better at higher levels.

“Thanks for taking care of Himiko-sama. This is something incidental, but I think you should take care of me as well.”

Two years after appearing as a sparkly ball of light in the Yamataikoku event, Iyo decided it was time to actually become a real Servant for us! As an AoE Arts Ruler, Iyo packs a surprising punch to slot into many Arts oriented teams.

Iyo is a farming Servant, first and foremost. With her Arts bonus from her Kidou (Ruin) and her unusual, for a welfare, 30% self-charge on Oracle of Darkness, she can loop most all nodes. Even without looping, she is a good damage dealer, combining those previous boosts with Priestess of the End’s attack boost and her Noble Phantasm, Yoiyami-Kageru Tsuki no Mitama C’s, stacking Noble Phantasm Damage boosts. Of course, that’s not to mention her great Critical damage. As she inflicts curse and has curse bonuses on her Noble Phantasm, she also can be a decent niche Servant for certain challenge quests.

Iyo’s biggest flaw is her lack of hard survival. While she does have a decent 4-star health pool and Ruler damage negation, she still will take every hit full force without external support. Her star generation is also a bit of a want. She also requires pretty heavy investment on supports to get her full usage.

Iyo is a great Servant for all Masters, as a 30% charge and AoE Arts Noble Phantasm can get a lot accomplished. She’d definitely fit best as a main DPS farmer. Just don’t call her a Rinface, she clearly has actual twintails instead of two sides up as a hairstyle!

Arts Looping

With a 4-hit Arts Noble Phantasm, an Arts up, and double Caster Altria support, Iyo is capable of looping all 3-3-x nodes except for Assassin and Berserker CE-less. With a CE like Ocean Flyer, she can loop all nodes. And if using double Caster Altria and Oberon, she can loop everything without even requiring 3-3-x. 30% Noble Phantasm charge makes a huge difference over the typical 20% that a Welfare receives.

Noble Phantasm Damage

As a welfare, Iyo has easy access to NP5, which already boosts her damage over a typical 4-star expectation. She’s got access to an Arts boost skill, but most important, she has a Noble Phantasm which increases Noble Phantasm Damage for 3-turns every time it is used. When Oberon is involved, this means that on her 3rd and final turn, Iyo will get a massive 60% boost to Noble Phantasm damage. All in all, it leads to massive numbers, some of the highest of all Rulers.

Critical Damage

When a Master looks at Iyo’s third skill which boosts Critical Damage for Wild Beast allies, they would think “That’s odd and useless.” However, Iyo has a hidden passive, Incantation of Kunu C, which gives her the Wild Beast Trait. That means she can have a 50% boost to Critical Damage for 3 turns, in addition to Oracle of Darkness’s 100% Critical boost for a turn on Arts cards. She’s going to put out big Critical numbers. 

Curse Niche

Every so often, there will be a challenge quest where an enemy has a huge amount of damage negation, and a Master is supposed to get them down with DoT damage. Iyo fits this perfectly. Not only does she have a curse skill, but she also applies curse every time she uses her Noble Phantasm, and doubles curse damage as well. This could result in some pretty silly curse damage numbers.

No Hard Survival

Iyo is missing any form of evasion, invincible, or even damage negation. Her Ruler classing does partially negate this as she’ll take half damage from knights and cavalry classes, but typically enemy Noble Phantasms are so strong that even that wouldn’t be enough to survive. She needs extra support if planning to eat an enemy Noble Phantasm.

Critical Gathering

Iyo has a slightly low star absorb rate, and can only general 10 Critical stars once with her third skill, which usually is used turn 1. Her Criticals will be strong if she can get them off, but she may not be able to do so. 

Support Investment

Sadly, Iyo really shines when she has two Caster Altrias to support her. With only one from support, she really falls off. She’s still a decent Servant, but she goes from a top-tier damage dealer to just one of many a Master could choose. She needs to loop to take advantage of the stacking Noble Phantasm damage.

Iyo primarily deals with looping setups, so she benefits the most with Noble Phantasm Damage Up CEs. However, her looping is sometimes just a little bit short in non-standard enemy waves or without Oberon, so she sometimes benefits from a bit of extra boost with Mixed Starting Gauge / NP Gain CEs. Her Critical star gathering is a bit of an issue, so she can benefit from Critical Gather / Critical Stars per Turn CEs.

• The Black Grail / Heaven’s Feel: If looping against 3/3/x non-Assassin/Berserker nodes with double Caster Altria, or against non-standard waves with enough enemies to refund with Oberon, Masters will want to boost Iyo’s damage as much as possible. The Black Grail is still king as a CE choice for this purpose. 
• Ocean Flier / Painting Summer / Magical Girl of Sapphire: If Iyo doesn’t have enough refund to use a Black Grail, she needs to gain it from her CE. Ocean Flyer is typically enough and gives the most damage, but most any with a starting charge CE, either Arts boost or NP gain boost will work. 
• A Tale of Love and Hope / The Star of Camelot / Dance with the Round Table / Avalon Celebrates / A Walk in the Park / Daddy’s Letter Show / A Fragment of 2030: Iyo struggles to gather Stars to herself. By giving her a CE which boosts her gather rate, or simply generates more Stars, she will deal more Critical hits. Masters should aim for a CE which either gives her a Starting Charge, higher NP gain rate, and/or Critical Damage to boost general damage as well.