"Frida's Dilemma" - "Negotiations" [Campaign 1, Mission 4]

Through the garrison, you can pass with the following army: 100 militia, 80 crossbowmen, 50 knights, 30 griffins, 15 inquisitors, and 5 paladins. With such an army, you can fight. Also, you meet a dwarf there, who gives you a quest to destroy hydras. After completing the quest, he leads you through a mine directly to the exit, which is guarded by lava dragons. You defeat them, and that's it. And, in my opinion, you don't necessarily have to defeat the phoenixes there.