I am interested in a good reference for reading about primes of bad reduction for the modular curve $X_E^{-}(N)$, which is a twist of $X(N)$ parametrizing all elliptic curves $E'$ whose $N$-torsion modules are anti-symplectically isomorphic to $E[N]$.
I assume they might be the primes dividing $N$ together with the bad primes of $E$. It would also be useful to see information about how the 'mod $p$' curve looks like at a prime $p$ of bad reduction and if it parametrizes anything.
