Rhea

"All I ask is that you guide these open minds with virtue, care, and sincerity."

- Rhea's instruction to Byleth upon choosing a House.

Rhea is a character in Fire Emblem: Three Houses. She is the archbishop and supreme leader of the Church of Seiros. At Garreg Mach Monastery, Rhea can help Byleth increase their rank in Reason, Faith, Brawl, and Swords. She possesses a major Crest of Seiros.

Profile
Rhea is the Archbishop of the Church of Seiros and leader of the Knights of Seiros as a result. She previously was Jeralt's superior when he was Captain of the Knights of Seiros until he left her employ in Wyvern Moon 1159. She serves as a key figure for the Officers Academy as well, assigning missions to the three houses each month.

Rhea is actually one of the Nabatea, the original children of the progenitor god Sothis. She is also Seiros herself, the saint who founded the Church of Seiros, defeated Nemesis, and helped found the Adrestian Empire. Seiros was a name she chose when carrying out these tasks, rather than her real name.

In the ancient past, the Children of the Goddess were born of Sothis's blood after the progenitor god arrived in Fódlan. She and the other children coexisted with the native Agarthans and shared their knowledge with them, leading their shared civilization to become technologically advanced and prosper. The Agarthans enacted various wars among themselves, eventually thinking of themselves as gods and turning on Sothis to try to kill her and the other Nabateans. Eventually, Sothis and the Nabateans defeated the Agarthans, but the war devastated Fódlan, and left most of the humans dead. However, unknown to the other survivors, remnants of the Agarthans fled into hiding underground, leading them to become Those Who Slither in the Dark.

Centuries or perhaps even a millennia later (it took a very long time for Sothis to restore Fódlan), Those Who Slither in the Dark convinced Nemesis, a bandit, to invade the Holy Tomb, where Sothis was sleeping after exhausting herself healing the land from the by then ancient war, in order to steal Sothis's body. From Sothis's body, Those Who Slither in the Dark supplied Nemesis with her Crest of Flames and the Sword of the Creator. Armed with the relic, Nemesis returned to Zanado to massacre the Nabateans living there to make Heroes Relics and crests from their bodies. Rhea was the only survivor of the massacre and was left one of the few surviving Nabateans.

Desperate for revenge, Rhea, now calling herself Seiros, wandered the lands looking for allies to oppose Nemesis and his forces. She allied with her fellow survivors (whose human forms came to be known as the Four Saints) and Wilhelm I, to whom she granted her crest, to oppose Nemesis in the War of Heroes, eventually killing Nemesis in battle at the Tailtean Plains and leading to the creation of the Adrestian Empire and the extended influence of the Church of Seiros with her as its head. The church rewrote history, hiding the existence of the Children of the Goddess, Agarthans, and the true origin of crests and relics, and revising the origins and allegiances of Nemesis and his crest-wielding allies, the Ten Elites. Seiros did this in the hope of maintaining peace, and tried to guide Fódlan as her mother would, but she never saw herself as adequate for the role.

Still awash with grief at the death of Sothis, Seiros secretly devoted herself to experimenting on implanting her mother's crest stone into created bodies in an attempt to revive her mother. Her twelfth creation, also a failure, had fallen in love with a man named Jeralt. As captain of her Knights of Seiros, Seiros, now going under the name Rhea, had transfused her blood into Jeralt after he took a near-fatal blow for her. This resulted in him inheriting a Major Crest of Seiros.

Her creation and Jeralt eventually sired a child; however, upon their birth, both mother and child were feebly weak and near death. As both were destined to die, the mother pleaded with Rhea to implant the Crest of Flames into her child. Acquiescing to the mother's dying wish, Rhea implanted the crest stone into Byleth, reviving them, but the mother perished as a result. Jeralt grew suspicious of Rhea due to the circumstances of his wife's death and Byleth's condition, who had a pulse but no heartbeat. Having lost his faith in her (questioning if Byleth's mother really died in childbirth) and fearful of what Rhea might be planning, he used a fire to fake Byleth's death and then his own. With the loss of his wife and child, Jeralt left the order of the Knights, secretly smuggling Byleth with him. It's unclear if Rhea believed Jeralt was really dead, or if she tried to locate him afterward.

Academy Phase
Years later in 1180, when Jeralt returns to Rhea at Garreg Mach Monastery after saving Edelgard, Dimitri, and Claude, Rhea asks for his child Byleth to become a new professor at Garreg Mach Monastery.

Rhea's true motive for this move was to keep an eye on the new professor in her hope that Byleth would be able to eventually merge with Sothis in both mind and body, in effect reviving the progenitor god and enabling Sothis to guide Fódlan once more. After Byleth's power fuses with that of Sothis, Rhea brings Byleth to the Holy Tomb, hoping to complete the transformation (namely to add Sothis' consciousness to Byleth's). However, her plans are shattered when Sothis does not revive and the tomb is invaded by the Flame Emperor and Adrestian Empire forces. The Flame Emperor is eventually revealed to be Edelgard, who previously used that disguise to hide the involvement of the Adrestian Empire.

Depending on the house chosen, Rhea's involvement in the story drastically changes.

Azure Moon/Verdant Wind/Silver Snow
In all routes but the Black Eagles, Byleth by default allies with the Church of Seiros and opposes Edelgard and the Adrestian Empire. If the Black Eagles were taught, Byleth still sides with Rhea unless certain supports and events with Edelgard were completed, in which case they may choose to protect Edelgard instead.

If Byleth sides with Rhea, Rhea is grateful for Byleth's alliance with her and requests their help in the initial defense of the Monastery against the Adrestian Empire's initial invasion. Despite the failure of Sothis being revived in the way she had expected, she still believes Byleth is in a sense Sothis, and tells them that if anything happens to her in the coming battle that she is entrusting the future of Fódlan to them. She also asks Seteth and Flayn to help Byleth and in effect also help Sothis. Although they are successful in repelling the initial attack, an even larger army commanded by Lord Arundel arrives, forcing Rhea to transform into The Immaculate One, her dragon form. Her attacks manage to stall the Adrestian Empire forces, but she is overwhelmed by Demonic Beasts.

Though Rhea ordered Byleth to remain behind, seeing her in danger forces them onto the battlefield. While Byleth is able to help her, Thales appears and hurls them over a cliff with an orb of Magic, leaving Rhea to roar mournfully. The loss of Byleth marks the beginning of the fall of Garreg Mach Monastery.

Crimson Flower
Byleth, desiring to protect Edelgard after learning about her past despite Rhea's orders to execute her, sides with the new Emperor of Adrestia, much to Rhea's despair and outrage.

Azure Moon
In the aftermath of the Fall of Garreg Mach Monastery, Rhea is captured by the Adrestian Empire, forcing the Knights of Seiros to join Byleth's forces to rescue her. After Edelgard's death, Rhea is found alive, but severely weakened. She steps down to live in seclusion in Zanado while Byleth takes over her role as Archbishop of the Church of Seiros.

Verdant Wind
When the Alliance defeats Edelgard and takes Enbarr, Rhea is found alive but seriously weakened. Claude is full of questions and urges Rhea almost angrily to unveil whatever secrets she has been hiding, but Rhea does not give all the answers immediately.

Rhea then accompanies Byleth and Claude as they travel to Shambhala and defeat Thales, the leader of Those Who Slither in the Dark. However, Rhea is gravely injured attempting to shield Byleth's forces from Agarthan missiles in her dragon form – which leads Claude to recognize she is the Immaculate One. In an even worse condition than before, she decides to reveal everything that she knows, and tells Byleth and Claude the truth about herself, the goddess, Agarthans, Nemesis, the Ten Elites, and the origins of Crests and Heroes Relics. Her fate in this route is left ambiguous, although considering her earlier claim of not having much time left during said exchange, it is implied she actually died.

Silver Snow
Rhea still accompanies Byleth as Byleth confronts and defeats Thales, and is still gravely injured attempting to shield Byleth's forces from Agarthan missiles in her dragon form. In this route, Rhea becomes berserk after revealing the truth and apologizing to Byleth, forcing Byleth to fight and defeat her in her dragon form. If Byleth has A-rank support with Rhea, she survives and steps down from her role as Archbishop to live in seclusion in Zanado. Alternatively if Byleth has an S-rank support with Rhea, she reforms the Church of Seiros in the epilogue with Byleth as her partner.

Crimson Flower
After failing to defend Garreg Mach, Rhea then flees to the Holy Kingdom of Faerghus and builds her forces there in alliance with Dimitri. After Dimitri is killed and their combined forces defeated at the Tailtean Plains, she seizes control of Fhirdiad, and as the Black Eagle Strike Force prepare to storm it, she orders Catherine and Cyril to torch the city. Byleth and Edelgard are able to defeat her forces, and face her in her Immaculate One form. Despite her power, she is eventually killed by Byleth and Edelgard. With her death, the Crest of Flames dissipates from Byleth's heart. While they lose the power of Sothis, their heart beats for the first time, restoring their humanity.

Personality
Rhea is what one would expect of a head of a church: benevolent, kind, and compassionate. While she is such to the devout followers of the church and the students and faculty of the Officers Academy, she is ruthless and dismissive of those who oppose the church with violence. While most of her Knights and Staff are followers of the Church, she does not force any of them to be devout followers, such as Shamir. Any who oppose the church with violence are dealt with by her self-righteous vision of justice and she even labels their defeats and misfortunes as judgement of the Goddess.

Deeply tormented by her Mother's death, Rhea is obsessed with the idea of resurrecting her, in part as a way to heal from her own suffering and return to the life she once knew. She also displays rather dishonest behavior having rewritten Fódlan's history to help her influence it, albeit with the desire to maintain peace. She knows that there is a mysterious group opposing her, but doesn't know who "those who slither in the dark are" nor their connection to the Agarthans until very late in the story.

In the Crimson Flower route, where Byleth, the bearer of Sothis's crest stone and consciousness, chooses to protect Edelgard instead of killing her, Rhea becomes increasingly unhinged by this perceived betrayal, eventually reverting to her vengeful Seiros persona and becoming obsessed with killing Byleth, believing them to have become a second Nemesis. She becomes increasingly tormented mentally in the years that follow, mumbling to herself and becoming such that even her closest friend Seteth loses faith in her.

However, in the Silver Snow and Verdant Wind routes where Byleth does not support Edelgard, Rhea maintains her sanity and becomes horrified and regretful of her actions, admitting in her S support that while she did desire to keep the peace she was also driven by selfish and immature motives, and that it was wrong to not recognize Byleth was a separate person from Sothis. She then hands over her authority to Byleth, as she believes she is no longer worthy of the degree of influence she had. That said, in their paired ending after she recovers her strength she returns to her position of archbishop as she and Byleth (the actual leader of Fódlan) work together to reform and prosper the nation.

Growth Rates

 * 45%
 * 35%
 * 45%
 * 40%
 * 40%
 * 40%
 * 30%
 * 40%
 * 70%
 * }

Maximum Stats

 * 86
 * 52
 * 65
 * 56
 * 56
 * 56
 * 43
 * 60
 * 97
 * }

Learnt Magic

 * D
 * Fire
 * Heal
 * D+
 * Bolganone
 * Nosferatu
 * C
 * Recover
 * C+
 * B
 * B+
 * A
 * Ragnarok Agnea's Arrow
 * A+
 * }
 * B
 * B+
 * A
 * Ragnarok Agnea's Arrow
 * A+
 * }
 * A
 * Ragnarok Agnea's Arrow
 * A+
 * }
 * Ragnarok Agnea's Arrow
 * A+
 * }
 * A+
 * }
 * }
 * }

Supports
Rhea can form a support with Byleth only. She can form an S-Support with both genders of Byleth.

Possible Endings
Rhea and Byleth
 * After finally saving both Fódlan and Rhea from Crisis, Byleth ascended the throne as the first leader of the United Kingdom of Fódlan. From her/his temporary residence at Garreg Mach Monastery, she/he endeavored to restore and develop Fódlan. Having narrowly escaped death, Rhea took time to recover her strength before returning to her role as archbishop. Upon her return, she applied herself to rehabilitating the church and helping those who had suffered because of the war. Thereafter, the two worked closely to forge new policies and achieve progress for Fódlan. The pair’s collective work came to be thought of as nothing short of miraculous.

Etymology
Rhea is a Greek titan known as the "Mother of the Gods." The name may also refer to the mother of Romulus and Remus, the mythical founders of Rome. Seiros may be derived from Seirios, Greek for "scorching", and an alternate name for the star Sirius.

Trivia

 * Rhea shares her Japanese voice actor, Kikuko Inoue, with Deirdre in Heroes.
 * Rhea shares her English voice actor, Cherami Leigh, with Mae and Emma in Echoes: Shadows of Valentia as well as Caeda, Gwendolyn, and Cecilia in Heroes.
 * Rhea is one of the characters who can have S-Supports with both a male and a female Byleth. The others are: Mercedes, Dorothea, Edelgard, Sothis, Linhardt, Alois (platonic) and Gilbert (platonic as well).
 * Rhea has unused growth rates and quotes, implying she may have been a playable unit at one point or may be a future playable character.