Warlock – “Expansion” [4th campaign, 2nd mission]

bonchik, you're probably not playing as the hero. Otherwise, you wouldn't have the urge to intercept ALL the messengers in the 2nd mission. There's nothing you can do about the defense. And at lower levels, the hero Railag should be able to defeat everyone, regardless of his stats.

Summoning is only needed when playing through the game in version 3.x. And even then, only when playing as the hero.