It's unclear how to complete the second mission: without attacking the purple player.
I buy passage from the guild, but a stack of harpies remains in the nearest garrison. I have to defeat them, after which a hero appears with a powerful army and attacks. If I defeat him, the mission fails. Of course, I could try to build up my army so that he doesn't attack, but that's unlikely to work. It's also unlikely that I can sneak past without a fight.
Is the mission impossible?