The first of 2 level 1 BF keys can actually be found early in the game, though it is well hidden. The second key is not too far past the 4 skeleton mages.
<span class='standouttext'>Spoiler : </span><span class='spoiler'>The first BF key is in a locked chest on the southern path in the starting cell block, with the key in the western spider cell in the arena.</span> (highlight the text to read)
