Worlds of Magic: Planar Conquest (UP)

There are 4 ways that a hero can be gained:

1. Pay for services at an Inn.
2. A positive event can randomly occur during a turn transition where they offer you their services for a certain amount of gold.
3. The Summon Hero/Champion spells.
4. Freed from a world feature where they were a prisoner.

I am not certain if all 4 ways will unlock this trophy but I can confirm that recruiting one at an Inn will cause this trophy to unlock immediately.