Dungeons and Dragons

I have a good core group of five players, but we're all adults, so it's pretty common that one, for whatever reason, can't make it to the session. I basically plan to run with four people, and which four it ends up being is always a fun surprise.

If a player's not here, their character turns into basically a non-combat pet. Not targetable, not interactable, not doing anything, just tagging along behind everyone and occasionally glitching through a wall. The character knows everything that happens in the presence of the group, they hear all the conversations, they know who we fought and who we saved, but they're otherwise a little intangible cosmetic. I'll post a recap in the Discord server before the next session (which reminds me, I have a recap to write).

The only exception is if the missing player has a thing that the party really would like to be able to take advantage of in session.

If the missing player was the one holding the McGuffin, and the McGuffin would be really handy to use here, their non-combat pet version hands it to somebody to use for a second and then takes it back. If the missing player had the Keen Mind feat and someone's trying to remember the truename of the Thief Lord they learned five sessions ago (which would be like three months in real time, since we play my game every other week), the non-combat pet chimes in with the answer and then goes back to being silent. If the missing player is the Cleric and someone goes down for good, the non-combat pet casts Revivify (on lair action initiative) and then vanishes back into the mist. If the party needs to get back to the wizard tower and the only one with Teleportation Circle has gone to visit their grandmother that weekend, Teleportation Circle gets cast.

If they have a power that solves or trivializes a challenge, which would otherwise be a massive pain in the ass (or a complete show-stopper), they use it and we go on. I'm not going to punish the player for not being here, and I'm also not going to punish the party for the player not being here other than the DPS/healing loss in combat (and, obviously, their contribution to social situations and their ideas for puzzle-solving).

The big thing I try not to do is not base anything super-important to the plot on any one character. They all have their personal backstory/patron quests, but they're all tied very loosely to the main theme of the campaign. It's happened before where I've had a session ready to go, and the events of the plot hinge on that character's backstory mic drop moment, and then they can't show up and I basically have to cancel the whole session. "This is the session where the Warlock finally gets to meet their real parents! And his parents are actually the bad guy's henchmen! And they know about a piece of his True Plan! So after the emotional, tear-filled reunion, they give the party the next clue on how to defeat the villain, and reveal what the McGuffin is good for! ....oh. The Warlock's grandma got COVID? He won't be here for... a while? Fuck. I got nothing."

Nowadays, it's more like "And this session is where the Warlock will finally meet their real parents! ...oh, Warlock's grandma got COVID? He won't be here for... a while? Ok, no problem; the parents are in the next town, and everything else that's happening in this town will just happen first." Occasionally I have to do some minor retcons, but it's not nearly as big a deal.