So, this might go against everything you have got planned, or it might work swimmingly. If it is the former, I shall remake the app.
Emily: The Spirit's Sonnet
A young looking girl in a hooded cloak, Emily is possibly the least overt of the current generation of Keepers, with the only striking figure being her molten red eyes that seem to glow in the dark of night. Or though, this works well, considering she is not a Keeper in the sense of a being that the Devourer created. She was instead a young casualty of the original world the Keepers destroyed. Having been slain and then brought back to life by a Keeper, she was imbued with great skill in magical arts, affiliating most strongly with Fire, but also having Earth and Storm at her disposal. These did not save her Master, as he was blown away by a rival Keeper, and Emily was left free to wander the lands. Which she did, until she happened upon a Keeper's pet that she found personally repulsive. A fight broke out, and the creature was nearly vanquished, by the Keeper who owned the creature arrived, and in a bout of sadistic torment, banished the girl to a frigid realm of demons and ice, to die the worst kind of death.
However, Death was not on the cards for the young Rogue Being, and so she was brought before a minor Warlord, and tricked him into being sacrificed to a Sung Spirit - a unique type of spirit that demanded both a song sung to attract them, and an object or being sacrificed to entice them - who called herself the Mistress of Magma. Together, the took over the small castle, and their power consolidated for several months, while Emily drew the metaphysical construct of a Sung Spirit Rune across the entire realm. Eventually, after fending off uprisings and invasions from other parts of the realm, Emily finished the rune, and began the Song of the 'Ignis Divine', the Godly Fire. While most songs simply had levels - Lesser, Greater, Grand, Noble - the Godly Fire responded to only one song, and was only enticed by a gargantuan offering.
The song was simple, and to the point. It lasted less than a minute, but Emily waited in her frozen castle for three hours, before the walls started to melt. After the first drop of unfrozen water hit the ground and immediately vaporised into steam, it took all of three seconds for the entire realm to burst into flames, and then from the ashes of destruction, the Flame King, Surtr appeared. He commended Emily on her voice, and the offering she had made. He then mused about how long it had been since anyone had been able to so much as reach his ears. Emily let him talk, because he was both old, and powerful, and both parties liked to speak a great deal. The King finished his monologue and looked to Emily, asking the formality of wither she wished to bond with him. She accepted, and became the host for Fire Incarnate, sharing her mind and body with him, as she had with the Mistress of Magma. Emily had expected the Lesser Spirit to be driven out by the King, but the meshed perfectly. Together, and yet apart. She had plans to summon a Greater, a Grand and a Noble Sung Spirit, but was warned against inviting too many spirits into herself so quickly, for it was a perfect way to lose your individuality in the sea of minds.
Emily accepted the King's words, and channelled the magic of the three to find a way to return to the Keepers and finish them with her new strength, eventually punching through from the now burnt lands of Kokytos to a new land, one unknown to her. She knew Keepers where here, but that was all. She would find them, and they would burn.