most tarantulas are, hmm.... Intense. they come off like vaguely violent shakespearean actors most of the time -- a lot of high gothic, gbb just has a tendency for going off into random speeches, frequent references to their beliefs about how the emperor shapes the webs of the universe. usually when you see a tarantula in town he's just wandered in on foot, covered in dirt, with an obvious Mission (even if that Mission is just poking around at your wares). some got more social braincells than others tho, which is why lyvar is "all weird and maternal" btw
lyvar is intimately familiar with the experience of being a tiny recently orphaned psyker child being found by astartes in the middle of a battlefield and it's made him really good at being the astartes in that specific situation. and psykers tend to be aware of other psykers, especially if they haven't quite learned proper shielding yet. so lyvar has, more than once, found some tiny recently orphaned psyker child on a planet and scooped em up and said, "CHAPTER MASTER CAN I KEEP THEM PLEASEEEE". and then he proceeds to be totally normal about it and not accidentally form a system where him being chief librarian makes him a sort-of-dad to the others, since he's the eldest librarian and has done a lot of their training
