4th) Make a monster based on your deepest fear
The Black Weight has chosen you. It calls to you. You can feel its yellowed eyes follow you from on high, its judgment on your shoulders like a glacier of lead. You must go to meet it. It calls for you and you alone.
The approach – The landscape has been changed. Great hands have twisted it out of shape, filled up with your waste: Burnt bridges, the ghosts of chances never taken, the dust of cares that never mattered, regrets in their churning multitudes, trashed time, could-have-beens. All the filth that has gone into your body, all the filth that has come out. The chaff and slop that has filled the waking moments before the coming of your death is dredged up and displayed to all.
Outside the lair – In the center of the wretched refuse of your life, it becomes difficult to breathe. From within that monument you hear the gleeful recitation of your sins; every hidden shame, every skeleton in every closet. They are the chains of truth upon your shoulders.
Within the lair – Unbreathable now, in the face of your depravity, your worthless flesh a stain and tumor upon the dance of physics. You stand within a palace built of the corpses of your dreams, nailed together by your laziness, your stupidity, your docility. You have let your body go to ruin, your sword dull, your mind tepid, your heart dim, all in the pursuit of the beastly Black Weight. It is strong and ever stronger for its feeding upon you.
You must defeat it. It will not kill you, but you cannot live with it continuing. You must defeat it. You have been chosen. Any still willing to give your carcass aid may do so, but you must deliver the final blow. A sword forged of a beloved’s hands shall offer some aid and comfort, but it must be swung by yours.
If brought to its knees, the Weight will plead, and beg, and take a most piteous form – but most importantly, it will remind you. Not just of what you are, but that it is needed. It is the anchor against chaos, the bulwark against the dissolution of self. There is no stability without it.
Strike now, strike now. If you do not, you will return to this pit, again and again and again forever and ever amen.
(Mechanically, stat the Black Weight as an adult or older dragon, replacing the breath weapon with weaponized existential depression targeting a single individual. The effected party member is the only one that can kill the creature, but doing so requires a series of difficult will saves or some killer RP moments.)