hello, poetry tag, how I have missed you.

A villanelle (also known as villanesque) is a nineteen-line poetic form consisting of five tercets followed by a quatrain. There are two refrains and two repeating rhymes, with the first and third line of the first tercet repeated alternately until the last stanza, which includes both repeated lines. The villanelle is an example of a fixed verse form.
-Wikipedia

Villanelles are a nightmare; there is no other way to say it.
-Craft of Poetry

( I've never tried to write a villanelle. )