Duncan x Adam : Man-At-Arms no more (Patreon)

When Hordak took over Castle Grayskull, he captured and transformed Duncan into his new personal general. As a test of loyalty, he ordered him to kidnap Prince Adam to use as an object of extortion against King Randor.

After taking the prince, Duncan took him to his dungeon to have fun with him.

This makes it clear that Duncan always secretly loved Adam, however as a soldier of Eternia and loyal protector of the royal family, he could not think that way about the prince.

now that his loyalties have switched sides... he can express his carnal desires to adam without guilt... the right and honorable man-at-arms is gone.