Should You Let Abhartach Bite You?
Let Abhartach bite you. It is the right call and it is barely a decision once you know what happens: you take a sliver of damage, Abhartach's fangs hit Arthur's blood, and the poison drops him on the spot. No fight. No risk. The afflicted refugees get their cure, and you skip a boss encounter entirely. Refusing only starts a trivial fight that ends the same way, with worse pacing and no upside.
Both choices hand you identical rewards, so this comes down to whether you want a clean two-second resolution or a pointless brawl. Take the bite.
Where this happens
The choice lands inside a dream dimension, one of the stranger places the questline takes you. There you meet Abhartach, a chained Fore-Dweller. He is bound, he is old, and he makes you an offer rather than an attack: he will cure the afflicted refugees if you let him bite you and take some of your blood.
The setup matters because it frames Abhartach as a bargainer, not a monster to be put down. He is chained for a reason, and he is asking for something specific in exchange for something you came here to get. The dream-dimension framing also tells you this is not an ordinary boss room; the rules here are not the rules of the waking world, and the chained Fore-Dweller is a piece of that older, stranger layer of Avalon's story.
Allow the bite
Say yes and the exchange plays out in seconds. You take minor damage as Abhartach bites you. Then Arthur's blood does the work for you. Abhartach is instantly poisoned by it and dies with no fight at all. There is no health bar to grind down, no attack pattern to learn, no risk to manage. The thing that asked to feed on you is killed by the very blood it wanted.
That detail is the whole point of the encounter. Arthur's blood is poison to a Fore-Dweller, and Abhartach learns it the instant his fangs break the skin. You walk away having spent a few points of health to end a creature that a straight fight would have made you work for.
Refuse the bite
Decline and Abhartach is enraged. A boss fight begins. It is a trivial one, well within reach of any build, but it is still a fight you did not need to have, and it ends with Abhartach dead just like the other path. You gain nothing by refusing except a few minutes of combat and the small chance of taking more damage in the fight than the bite would have cost you.
There is no hidden reward for standing your ground here, no lore beat you miss by taking the bite, and no consequence that makes the fight worth choosing. It is the long way around to the same door.
Identical rewards, either way
Whichever you pick, the loot is the same. Both options award the Fore-Dweller's Bauble, a magic focus, along with the rest of the encounter's rewards. The afflicted refugees are handled the same way too: one afflicted Keeper recovers, while a second patient stays catatonic. That second patient is not a loose end you missed. It sets up a later decision in the quest, so leave it be and carry on.
Because the rewards do not change, there is no min-maxing angle to this choice. You are not trading loot for an easier fight or sacrificing a drop by taking the peaceful route. The bite simply skips the combat and gets you to the same destination faster.
The verdict
Take the bite. It is the cleaner, faster, and slightly funnier outcome, and it costs you nothing but a few points of health. Watching Abhartach drop himself the moment he tastes Arthur's blood is the encounter working as intended, and it gets you the Fore-Dweller's Bauble and the cured Keeper without lifting your weapon. Refuse only if you genuinely want the fight for its own sake, knowing it changes nothing about the outcome or the rewards.
Either way, keep an eye on the catatonic second patient. That thread comes back later in the quest, and how you handle it then is the decision that actually carries weight.
For how this fits with the game's other branching choices, see the choices and endings hub. For where the quest sits in the overall order, see the walkthrough.