Learn Turkish: Aç kurt kapkaranlık gecelerde sürüye saldırırmış. - The hungry wolf would attack the flock on pitch-black nights.

The ending -mış added to the aorist (saldır-ır-mış) shows that this is something heard from others, a legend, or a general tale rather than something the speaker witnessed firsthand. While saldırırdı (aorist + past) also means 'used to attack' or 'would attack', saldırırmış adds a storytelling or 'rumor has it' flavor, which fits perfectly when talking about wolves in the dark!

Why does sürü (flock) take the -ye ending here?

The verb saldırmak (to attack) always requires its target to be in the dative case, which shows direction. So, you add the dative ending -(y)e to sürü, making it sürüye (literally 'towards the flock').

How does kapkaranlık get its meaning of 'pitch-black'?

This is an intensified adjective. To emphasize a word in Turkish, you often take its first syllable (ka- from karanlık), add a consonant like p, m, r, or s (here it is p), and attach it to the front. So, karanlık (dark) becomes kapkaranlık (completely dark, or pitch-black).

Why use gecelerde (on the nights) instead of just saying gece like we often do for 'at night'?