Sitri was not just lending money... she was investing
where did this debt even come from
Krai kept buying relics to compensate for his weaknesses and some are super expensive especially on auctions.
not for his weaknesses, he is actually a collectors so he enjoy seeing relics, just like when he want to buy Gilbert's sword. He just getting carry away from time to time.
Yes, that is what the people in the anime think. When in reality he just likes them because he doesn't want to die.
in the manga at least, he said it himself he enjoy to look and use relics, the anime seems to cut out the "Tear of Truth" relic which they want to use to get information out of Krai, which he is excited about because he get to see that super rare relic again.
He is pretty weak after all, even if he collect all the weapon's type relics, he has no strength nor skill to even use them.