Each person is bound and chosen for each gem to be the protectors of the gems. each gem holds sinful powers beyond any control of normal humans, let alone a demon or other specimen can know the limits they contain. the gem is fueled by the holder's bound sin and only grows strong the more the sinner commits more acts of the sin. 

once lifehacker found the sin gems, they went to Fallen angel (the spades) and asked them about it. Fallen angel explained about the sin and virtue gems and how they're destined to be bounded to a holder. once lifehacker found these gems, they wanted to find the ones that these gems would burden and bound to with the attempt to help them, whether by breaking the tie of getting connected to the gem or helping them live a disciplined life while maintaining the gem's influences. 

if all the gems were to be held by one person, forbidden sinful powers are unlocked to rule over all of the underworlds combined; corrupting souls by the touch and can topple the paradises to fall down. but the ones bound would become more corrupted and possessed to be titans of destruction and corruption. there is almost no hope to save those bound once they become fully corrupted.