The text/story used in this is taken from a variety of sources. Primarily, from the elegy of the end weapon description.
The rest include, crimson witch of flames set, Defender's will (Rostam's set), Pale Flame (stainless bloom) and the Shivada Jade gemstone (quote from Tsaritsa)
Tsaritsa, Pierro and Rostam are all fan made! But Tsaritsa's design is based on the herrscher of ice from honkai