Complex sentence: During one attack, Hiccup believes he has shot down a Night Fury, an extremely dangerous dragon, and later finds it trapped in his bolas but finds himself unwilling to kill it and instead cuts it free.
Split into simpler sentences: During one attack, Hiccup believes he has shot down a Night Fury, an extremely dangerous dragon. Hiccup later finds it trapped in his bolas but is unwilling to kill the dragon and instead sets it free.