I continue running a campaign on myth-weavers.com and we're using Hackmaster 5e but planning on soon converting to AD&D 5e. The campaign's been running about four months and has been moving forward rapidly. Characters currently vary from 5th to 10th level. Yes, they've advanced rather quickly. For context, we're playing a no-level-limit campaign.
When I started this play-by-post campaign back in April 2022, using the Mythweavers site, I substituted some place names and proper nouns, to hopefully throw off any meta-gaming player from discerning the published source of the story-arc: Night Below, a well-received product of the AD&D 2e era. Of course, some of the players are in their fifties like me, so may guess it anyway.
Currently, the PCs are about to wind up the first portion of the campaign arc, at which point they'll have the option of retiring either permanently or semi-permanently. Having saved Haranshire Slaytonthorpe from the bandit threat, they've earned the gratitude of the locals residing in Milbourne Millboro and Thurmaster Trimaster, including that of the mage Tauster Tauste.
I'm using a doom clock in the current fight, which is against the BBEGs. The PCs are fighting death cultists and giant skeletons in a Fane that sits atop the mega-keep, The Brokenspire Tornspire. A group of bandits have been kidnapping people from various surface villages, towns, and cities for the past few in-game months. The PCs have fought against these bandits in the region of Slaytonthorpe.
In the current battle, a winged monstrosity I've given the appellation draco-demon is using a fiery breath weapon to soften up party members. More importantly, it has begun to glow and throb with an intensifying inner light that signals an imminent explosion. A danger clock is ticking. Each round, I select a party member to roll a dice pool. If three or more of the rolled d6s comes up '6', the draco-demon explodes for 8d6 penetrating damage in a fifty-foot radius. The dice pool started at 3d6, but will contain 4d6 next round, 5d6 the round after that, etc. It's a tension-building mechanic...
Assuming that the PCs -- who style themselves The Knights of the Rising Phoenix -- prevail, they will bring the current story arc to an ending and will have the undying gratitude of the people of Slaytonthorpe. Perhaps they'll retire. Then again, they may follow up on clues that this recent rash of kidnappings of surface-dwelling spellcasters may be occurring at the orchestration of a much more dire intelligence in the Underdark...