Final answer:
The correct answer is c) loyal, as it matches the description of someone devoted to the royal party and aligns with the character traits mentioned in the provided texts.
Step-by-step explanation:
The most suitable adjective to fill in the blank is c) loyal, as it is consistent with the description of someone who is 'devoted to the royal party' as well as the passages provided from different texts. Each of these passages emphasizes the character's loyalty and commitment, whether to the law, their country, or their sovereign. The texts highlight the character's virtues, such as being hardy, wise, just, honorable, and stable, which align with the characteristics of loyalty.