Again, I say: It's showing you content, then actively punishing you with a "reset and reload until you succeed" dead end if you choose to actually pursue it, while giving you full rewards for ignoring the content and killing it without engaging. The "Best" solution is to ENTIRELY skip, ALL the content placed here, and to walk up to the Illithid and Ctrl-click it (external to situation game mechanic), without ever even talking to the fishers. This yields the best and most optimum outcome, with zero risk of punishment or failure. Defend it how you like: it's objectively a failure of design. Context is literally irrelevant in the face of these facts.

In talking about how you'd love to do it as a DM you're also highlighting an additional design failure - Everyone else just stands there and watches you feed your head to the Illithid and does absolutely nothing, and there are no options or prompts for them to do anything, in any way.

They give you this situation - an entity that knows literally everything about your situation, why you're in it, and what's been done to you - and given him to you in a severely weakened, crippled and dying state. Yes, they've illustrated that he's dangerous - that doesn't change the fact that what is being presented is an opportunity that a reasonable player could expect to turn to their advantage in some small way. Except, you can't, and you're punished for trying at all, and rewarded for not doing so.

Here's what would stop it from being a failed design:

- If the checks involved were not multi-tiered all-failstate checks. That's garbage design to begin with.
- If succeeding in your efforts won you something of value (information that could lead to further dialogues, perhaps, or something nearby that the Illithid had hoped to find in the wreckage that would have helped him and can now help you, maybe).
- If failing in your efforts put your party into combat. The failing player is stunned/charmed, the others can roll initiative and react, The player, on their turn, will 'help' the Illithid, who stands, and the Illithid, once helped and on his own turn will use devour brain on the victim character (auto success at that point). The party have until that happens to either remove the player from the scene or break the effect, or stop the ilithid, and it's only if they don't do one of these things that he grains his full health, kills the player and wipes the party.

Now you have a situation that promises a reward for risk, delivers something of value if it is chanced and succeeded at, leads to danger and consequence for failure, and actively engages the players to win over the situation by their own choices. It can lead to a party wipe on extreme failure or poor choice making, but still allows the players to experience the content, even on partial failure, and come out alive, albeit without the value they had hoped to gain from the risk.