It's true that Lahabrea knows little of Byleth. But neither does he bat an eye as Byleth all but sets to tearing on of the intellect devourers apart. Now that his spellwork is done, there is nothing more to do save to eliminate them as swiftly as they are able.

It is, still, a relief to feel the magic hold though. The keening whine as the creature dies is still not pleasant, nor is the feeling of its deathknell pressing up against his magic. But it is manageable. Far more so than suffering the immediate aftermath, and it's with a nod in return that he sets upon the intellect devourers in turn.

He own attempts are more more methodical, perhaps, than Byleth's. He calls flame, and it answers as surely as it ever has, manifesting as immolating pyres that one by one pick off what stragglers that Byleth doesn't see to.