Bolvi is introduced through an encounter with a woman that he has fallen in love with in just a few hours, Kenna. She's barely a third of his age, but he's so in love with her, and she seems to be so in love with him. She convinces him that the two can be married as soon as he gets a Summoning Stone, which is conveniently owned by a small band of humans who just want to hide it away. Only after he's killed them and taken the stone does he find out that he's been tricked.
Abua Shi's introduction is similarly bad. He's tricked into taking a summoning stone. A guard attacks him. Only after he kills the guard does he realize that it was his wife, bringing him the stone, and that she'd been concealed by an illusion.
In general, if a Summoner is tricked into getting hold of a Stone, you can guarantee two things: they're going to do something morally questionable during their bio, and something sad will happen to them.