This is a topic about which I’m still very much unsettled. It’s the idea that PCs engage in activities which very much involve adventuring, yet it all happens off-screen. How best to approach this, if it’s going to happen?

This is actually present in the early system rules.In 1e, Gygax speaks of spying missions, complete with tables to help adjudicate them. He speaks of assassinations, also including tables. Those tables generate the results of the activities, though, as the activities aren’t played out at the gaming table.

Granted, one could always just use those tables for use with NPCs assigned to spy or assassinate a foe as part of high-level play, without a PC getting involved. there’s no written instructions as to that being the intention, though, which leaves the door open for it including PC activity. When one also considers that Gygax described PCs being out of play off-screen while journeying to consult an oracle, it’s easy to see that off-screen play was part of how things were done. Ergo, we should expect off-screen activity as part of play; the only question is what activities should reside off-screen.

Just riffing on what Gygax has describe, I reckon information-gathering of many sorts would be good options. Consulting with oracles, scouting wilderness areas for basic information on what resides there, spy missions into foreign towns and cities to get the lay of the land before arriving, and so on. Put specialist PCs to work doing their specialist things: send thieves to scout out that city, a hunter or scout to get a general sense of the land beyond that mountain pass, a wizard scrying the area where a transfer portal opens on another plane, and so forth.

This is all stuff GMs can certainly do on their own. I think it would behoove designers to provide guidance and support for it, though, as what the system expressly supports typically appears in higher quality than if it’s just something mentioned as being possible in passing. I know that I’ve very rarely had a player ask for such an off-screen jaunt. I don’t recall any happening at the tables I’ve played at. I suspect it’s not something that is regarded as a normal part of play, in a wider sense.