Maybe they can even control them so precisely that they could block sunlight for an entire part of the planet. Like blocking the sun above China or something like that.

Even if they only managed to block 25% of the sunllight, it could be enough to disrupt the power grid because sun farms would produce 25% less power, or do it for months and disrupt the harvest. Just some random ideas that just hit me. Maybe not used alone, but as part of a bigger strategy/attack.