As an impending doom

Write a series of increasingly bad events, ending with some final doom.

Start by imagining the final, ultimate bad thing that can happen and write a short description, like "The throne room collapses." Then, write 1-4 grim portents, events that represent how the hazard starts and how it escalates. Pair each portent with damage and tags, if appropriate.

Put one or more check boxes next to each grim portent (multiple check boxes means that portent happens multiple times). End with the impending doom. In play, when you make a GM move, you can advance towards impending doom and have the next event happen.

Optionally, you can write triggers that cause the doom to get closer. The trigger might be fictional ("each time there's a loud noise or powerful blow") or mechanical ("each time someone rolls doubles").

During play, consider making the number of check boxes in the impending doom public. This can ratchet up the tension and it lets the players make decisions based on how much time they have (or don't have).

Sajra the swyn's lair is an old Green Lord tomb, buried by ages of forest growth. One of the chambers features a cracked, sagging roof held aloft by three ancient wooden pillars (and a fourth that collapsed many years ago). Some of Sajra's crinwin have started building nests around the remaining pillars, further weakening them.

The PCs are likely to get into a fight with the crinwin in this chamber, and the pillars could easily be harmed and start collapsing. I write up the hazard like this:

UNSTABLE PILLARS: Advance this each time a pillar is struck, or as a GM move.

• O Pillar cracks/buckles, dirt pours down
• O Stones fall (1d6+1 damage, forceful)
• OO Pillar breaks, stone slabs fall (1d8+3 damage, area, forceful)
• O IMPENDING DOOM: Ceiling collapses, burying anyone still inside (Death's Door); connecting tunnels blocked off