Edrmari's Letter

A small birds arrives, a letter tied to her leg. She is obviously here to deliver the message, and hops about disoriented when it is untied. She flies off while you read the letter.

full size by mag_e

I would write some pleasantries about how we wish this letter finds you well, but we both know what is coming. So instead I hope this letter finds you aware of the armies of monsters making their way towards Rhina. If you are not, simply discard this letter, because clearly you are not who we had hoped. Arrive at the city of Thi as soon as you are prepared. Ready whatever armies you have before you go, or they shall be defenseless. Time is not on our side, though, so come quickly. Thi has spoken briefly of a victory. Here it is in short, think about how to solve it on your way: whatever makes it to Rhina will have to be fought off, but we may be able to fortify our plane from the others to prevent more intruders. We envision a sort of moat in the Sea, so the other planes cannot reach us, but creating it is just short of impossible. Every option must be considered.
-Edrmari

You have been summoned. But who are you, and what great power or legends do you hold that have gained the attention of Thi? What makes you one of the heroes who could save Rhina? Are you even a hero?