Walkthrough of the Life campaign on Champion difficulty.

The battle can be challenging, but only if Lysander hasn't leveled up his warfare skills. For a good playthrough of the first scenario, it's quite sufficient. Apply various buffs to your units, and you're good to go. But the main thing is to prevent the tank from being attacked by everyone at once – it won't withstand it. And don't let the hero die and be resurrected – the buffs will be lost. I don't remember the details of the walkthrough, but on the standard level and on the champion difficulty, they can differ significantly.