Sentence:  Theon Greyjoy is the most well developed character on that stage, and the action comes down to him. Euron, with Yara underneath his ax, goads Theon into attack. But Theon is <WSD>overwhelmed</WSD> by the violence all around him, and instead he jumps overboard. 
Meaning of the word marked with <WSD> tags:  To overpower emotionally.