Ah ballads. I love how flexible the meter in these tend to become, as is also evident by yours serpent. First stanza follows iambic meter, second kind of a dactyl, third Pyrrhic and spondee and so on and so forth. Now some might not like that each stanza sounds unique, but I for one like it. Intentionally or not, you've managed to use meter in order to increase the tempo of your story. Like, if you wanted to bring more action, you used a meter with more stressed syllables. If you wanted to create a mixed tempo, you used a meter with more unstressed syllables. Keep in mind when you're writing your next ballad to match the right meter with the right tempo. Nobody wants to read stressed meter when someone is sleeping, but you've more or less got the essential part of a ballad down; that is matching meter with context.
Now, even though the attempt at creating different metered stanzas was nice, a few lines in these stanzas don't properly follow the meter. Nothing major, but it very slightly sounds awkward. I noticed most of the ending lines of the stanzas go a bit haywire with respect to the stanza's meter. This is fine if you want to intentionally add more emphasis, in fact that is a good method; but I don't think that was your intention.
Your choice in figures of speech felt...unique. Stuff like "oh wait, there's a catch," and repeating the same meaning again in the next line, etc. I'm not saying its bad, every poet has their own signature style, so maybe these as your own unique style. Still, always try and add flair to your poem.
Coming to the context, I do get the feeling of epicness from this ballad, which I think was your aim so good job on that. If you would've refined the meter a bit more, and used more "epic" sounding figures of speech, that would've been better, but overall a really good attempt for a first-timer.
Also, ballads were originally meant to be poetry-song hybrids danced to at a ball, so if you want to be more contemporary and traditional try adding refrains and a song like rhythm, similar to what one does in villanelles. This modern method of ballads is fine too, though. I just have a personal preference of following the 'old ways' of poetry.
