Heart of Gold level 1 - Wizard dead on sand

So I killed each version of the wizard, and I've destroyed every gate. However, the final version of the wizard died on the sand near the invincible hero gate and my imps can't pick him up.

Is this an error? Looks like there's no way to complete the level.

Also, the invincible gate has summoned literally 100s of level 7 heroes who are just standing next to it. No joke, there must be over 200 there. I had to close the same as so amny were spawning my PC couldn't handle it.