"...a lot. They can tell whether there's a Yeerk in someone with mindreading from a variety of ranges, blocks to up to miles, those of them with that ability, and pick up surface thoughts from us and the host alike. Generalized spellcasting has offense including lightning and fireballs and demon summoning, assorted defensive shields, trap spells. Some spells can be applied to artifacts and carried by other people but need recharging. Their strongest thoughtspeakers have a range of a few hundred miles; there's a longer-range spell the casters can use. There's a separate ability that can telekinese or teleport things, increasing in difficulty if they're going far or the thing is heavy. There's an especially rare ability that is called 'mind healing' but like the biokinesis healing is better understood as fairly general mind editing; there aren't many of those but Leareth's second in command has that and the general spellcasting one and my host is terrified of her. - in a general sense; they have good unit discipline. Both the casters and mind healers can force people to do things, including Yeerks separately from hosts and vice versa, possibly in ways that persist on a host after infestation but fortunately mine right now can't explode."