Karel from Fire Emblem

Appears for the first time in  Fire Emblem Rekka no Ken's ("Fire Emblem Blazing Sword")Ch.25: Pale flower of Darkness.

The snow will stop right after Nils tells you it will. Then Nils warns you that the snow will start up again. When it starts up again a Blade Master named Karel will appear in the top left corner just under where the Druid was. Talk to him with Eliwood and he will join your cause. Little tip: if you do get him, use him and Lord pent to kill Kenneth.

Here, some of his support conversations:

-I-
GUY:    Y-You...!
KAREL:  ......
GUY:    Hold on! You're Karel, aren't you? You're the Sword Demon...
KAREL:  ......
GUY:    Oh, forgive me! I am Guy, a warrior from Sacae. I would like you to
        teach me the art of the sword!
KAREL:  ......
GUY:    Hm! What's with you? Why don't you--
KAREL:  Be grateful for your inexperience. If you were stronger... I would cut
        you down where you stand.
GUY:    I... I don't... What's your problem!?

-II-
GUY:    Master! Wait for me! Master Karel!
KAREL:  ......
GUY:    Please, I implore you! Teach me the art of the sword! I want my name to
        be known far and wide in Sacae!
KAREL:  When my fame first spread in this land, many worthless dogs aspired to
        swordsmanship. Then they all fell, one by one... Forget it, pup. Leave
        my sight.
GUY:    D-Don't go! You want someone to fight, don't you? Then make me your
        opponent!
KAREL:  ......
GUY:    I know I'm not good enough to fight you now. So, just train me in the
        sword. In one year's time, I swear I will master the art. Enough to
        match you--enough to best you!
KAREL:  ...... You seem to mean it, don't you?
GUY:    Y-Yes!
KAREL:  Very well. From tonight, we begin your training. You will learn the
        sword.

-III-

GUY:    Master!
KAREL:  ......
GUY:    Master! How goes my training?
KAREL:  ......
GUY:    I really think I am getting the hang of it. Maybe I'm, you know, gifted
        or something? I'm still no match for you, but soon...
KAREL:  Guy.
GUY:    Hm?
KAREL:  Your training is over.
GUY:    Huh? Why?!
KAREL:  You are strong enough. If I teach you any more than this... Then I will
        have to cut you down where you stand. I would cleave you in two before
        you could take a single breath.
GUY:    ......!
KAREL:  Even now, I can barely restrain my blade. It longs to bathe in your
        blood, to test your steel. The thought alone makes my blood roil.
GUY:    M-Master!
KAREL:  Leave. Never speak to me. Forget your offer to seek me out in a year's
        time.
GUY:    M-Master! Thank you! I owe you so much. But when I said I would
        challenge you, that was no lie. I will grow stronger. I will beat you.
KAREL:  ...So be it. When next our swords cross, we will see. Let us meet one
        year from now. Then I will know your skill. Until then.
GUY:    ...... Yes...Master.