Gambler's Ruin is a quest in Bastard's Wound.
Rostrom Lenk believes that Mell, the Wound's bookie, is cheating. He asked you to investigate the matter.
Rostrom thinks the best place to start is by questioning Mell directly. As a Scribe, he should recognize the authority of a Fatebinder and respond with truth.
- Talk to Mell. You can use Athletics 52, Subterfuge 57, or the Lawbreaker background to make him come clean or go and talk with Telesophia (note that you need to use the speech checks when they come up, otherwise the option is gone). It's also possible to shut the betting ring down by invoking Kyros' law (or rather, its flawed interpretation).
- Telesophia will ask you to kill Argaen before she spills the beans. You can arrange for a meeting in the Shattered Bastion, where you can kill him without repercussion or tell him to leave so you can deceive her.
- Either way, you will learn that Tonves is killing the beasts in the Oldwalls to skew the win rates in his favor - and Mell is profiting from it, more from fear than genuine greed, as he claims. He will give you his keystone and direct you to the southernmost portal in the Wound (the one on the island right of center).
- Enter the room and examine the beast, then search it to find the Forge-Bound armor fragment. Return to confront Tonves. He will reveal that the whole operation was Jaspos' idea, but not to gather rings, but to provide bone and teeth for his water purification procedure. Mell turned the situation on its head, in order to satisfy his greed, demanding that Tonves kill strong Beasts in order to buck the odds and get rich.
- Tonves will split and hide in the Fractured Depths, while Mell will become the next objective. Talk to him. You can decide the situation:
- Use Athletics 52 to extort Mell.
- Exonerate Tonves while condemning Mell.
- Exonerate both, but advise caution
- Demand a stop to scheming, but let gambling continue.
- Dismantle the gambling ring on pain of death.
- Return to Tonves in the Depths where you initially found the body and inform him of your decision. Doing so completes the quest.