Repercussions of recklessness

In $town you may meet a young woman named Tirra Stalvino. She’s a successful writer and built her career on adventure stories. She will ask you if you are an adventurer and tell you about her lost father.

My father disappeared back when I was six or seven. He was in the guild of mercenaries,
but his pay was meager and my family struggled to make ends meet.
One day he said he was going on an adventure that will bring enough money to live comfortably
for years, and never came back.
My mother thinks he just made up that story as an excuse to abandon us,
but I'm not so certain and I'd like to know what happened to him.

I've seen him collect potions and recharge his enchanted weapons before he left,
and he promised we would no longer struggle when he succeeded. He seemed to believe his own words at least.
He said he was going to find the Flaming Sword.

All I know about the Flaming Sword is that it was made for fighting demons and was held by the Temple's crusaders,
but the Temple doesn't list it as a lost relic, which only seems to confirm my mother's suspicion.
I'd like to find out his ultimate fate still.
I have no idea where he went, but maybe his former superiors in the guild know more.

If you agree to help him, head to the Guild of Mercenaries. Luckily, the current head of the guild branch in $town is an ex-superior of her father. She will tell you:

Jin? I never thought I'd hear that name again, but of course I remember that loser.
His fighting skills never really progressed, but his ambitious certainly did.
We never assigned him anything but simple escort jobs where we were certain
he would most likely not need to fight at all.

One day he came to me and said we'd soon see what he was capable of.
I don't know what exactly he meant, but we have never seen him again.

Mention the Flaming Sword to her and she will remember some details:

Oh, that one... Around that time, there were rumors that a whole party of crusaders
perished on a mission to cleanse an old castle from dark god worshippers and demons.
Their leader allegedly carried the historical Flaming Sword, a relic of the crusaders' order.
The Temple never officially confirmed it, but I suspect that castle in question
might be Eagle's Nest.

If you ask rank-and-file crusaders about the sword, they will just tell:

The Flaming Sword is the ultimate weapon for fighting demons.
I've never seen it, the official position of the Temple is that it will only be used in case
of a large-scale demon invasion and is too valuable to use casually.
We have run-off-the-mill swords enchanted with a fire spell for daily use,
and they indeed work well enough.
Our revered grandmaster may be able to tell you more about that sword.

If you ask the grandmaster about the sword, he will not tell you much else, but mention Eagle’s Nest to him and he’ll tell you a story:

So, you've heard that the Flaming Sword was lost? Our tactic of simply not talking about it has been effective
against any possible rumors for a while... That sword is indeed lost, but we prefer not to draw attention to it,
not just to save face, but also to keep more people from dying in futile attempts to recover it.

I even know exactly how it was lost. I was there. There was a demon infestation in the Eagle's Nest castle,
far to the south, high in the mountains. Most demon infestations are nothing special, just a couple of demons,
but that one was reported by travellers rather than owners — presumably, the owners were no longer alive to report it,
and that was worrying.
I was the youngest member of the squadron and I was to stand a watch at the entrance and keep demons from escaping.
They used the then-usual tactic: the commander drew the flaming sword and they charged head on.
At first they head an upper hand, but then suddenly a herd of demons flooded the hall.
That was the moment when I lost my nerve and simply ran away. I waited for a few hours hoping my peers would come back,
but they didn't. I simply walked back to our headquarters and told them what happened.

A year later, an adventurer came to me to ask about that castle.
He heard the story of a whole squadron of crusaders that perished there and lost a relic,
and he hoped to become famous by recovering it. As you can guess, I haven't heard of him since then.
Don't go there. You'll just get yourself killed. I'll mark it on your map so that you know where not to do.

You don’t plan to follow old grandmaster’s advice, do you? Head to the Eagle’s Nest castle. You will find that the gate is locked, so you’ll need to either pick the lock or levitate over the wall. In the courtyard you will find a lonely man — that man is Jin Stalvino. He will

Have you come to rescue me? They've been keeping me as their servant for the last fifteen years!
Those cultists and demons! They make me do all the dirty work and they also make me...
No, it's too horrible, I can't even talk about it!

What, my daughter sent you? I remember it like it was yesterday, she was just a little girl at the time,
and she was crying and yelling: "daddy, don't go, you will be kill by demons".
What a fool I was. Soon I wished they killed me, but they had another plan.

See, there may be a way to defeat them. The cultists gained posession of the castle by tricking one of the inhabitants
into bringing a cursed item inside.
The problem isn't how many demons are here, it's that the cultists can summon unlimited reinforcements.
There's only one weakness in that scheme: demons can't summon other demons, and most cultists leave for the day.

The cursed item is an antique lamp, it's kept in the room on the upper floor. You may be able to reach its balcony
if you have a good climbing ability or can levitate. If not, you'll have to fight your way up, but at least you'll know there's
a finite number of demons to defeat as long as no humans reach that room.

If you can reach the upper floor directly, that will make your battle a lot easier. The room is almost right next to the balcony and it’s guarded by two moderately powerful demons. Kill them and pick up the lamp, then proceed downstairs and kill all demons and cultists you see. The Flaming Sword is also in that room.

There are two powerful demons in the dining hall, but they are positioned in a way that makes it wasy to get them to fight each other instead of you. Run across the hall to provoke them into firing spells at you and there’s a good chance that they will hit each other. Watch their fight, then finish off the greatly weakened winner.

If you have to fight your way to the lamp room from the main entrance, you need to be careful. Once you enter and start attacking, the cultist in the middle of the dining hall will run upstairs, pick up the lamp, and summon a large number of demons. If you go that way, make sure to kill that cultist first.

Once you have the lamp and the Flaming Sword, and everyone in the castle is dead, return to the hapless father in the courtyeard and escort him to $town. His daughter will be happy to be reuinted with him.

You can then take the lamp and the Flaming Sword to the grandmaster of crusaders and he will arrange the ownership of the Eagle’s Nest castle transferred to you.

Notes

The names of the quest and of Jin Stalvino and the ungrammatical phrase “you will be kill by demons” are references to the infamous “DOOM: Repercussions of Evil” short story.

The dining hall with two demons that you are supposed to get to infight is a reference to a DOOM2 map and the usual DOOM tactic in general.