With regards to overlapping air envelopes in Spelljammer, if you have a smaller ship and want to investigate a relic is there some way to verify that the air envelope is not deadly before you take your ship in closer? I did not see any way to do that?
I intend to mange this in two ways. (1) is to have some sort of "Detect Air" spell for player characters (I'm not sure if such a spell exists in any previous edition, but seems practical enough), and (2) I'll assume that just as the Spelljammer in the helm can detect to some degree the nature of objects a near their vessel, they can also in some way determine the status of the air envelope. A perception roll seems simple enough a solution in that case.
With regards to overlapping air envelopes in Spelljammer, if you have a smaller ship and want to investigate a relic is there some way to verify that the air envelope is not deadly before you take your ship in closer? I did not see any way to do that?
Any creature inside a deadly air envelope that attempts to breathe will immediately discover that it can't. This means absolutely anyone can drive up next to something they want to investigate and send any creature into the adjacent envelope to check and report back. Exact methods for doing so will vary by access to minions and desired range, but e.g. you can use Find Familiar to do it very easily. Remember, Deadly Air can't hurt you with 30 seconds of exposure or less, so even a very fragile minion can check, and with a functional fly speed of your Intelligence score in grid spaces, even a basic Int 8 to Int 10 crew member will have a fly speed of 40-50 feet, which means it won't take all that long, and you don't need to get perfectly adjacent to the other envelope to check it. These envelopes are transparent, so you can signal the ship with body language (e.g. waving a flag) even before you report back to the ship, if you're the reporting minion.
With regards to overlapping air envelopes in Spelljammer, if you have a smaller ship and want to investigate a relic is there some way to verify that the air envelope is not deadly before you take your ship in closer? I did not see any way to do that?
https://www.dndbeyond.com/sources/sais/aag/astral-adventuring#OverlappingAirEnvelopes
I intend to mange this in two ways. (1) is to have some sort of "Detect Air" spell for player characters (I'm not sure if such a spell exists in any previous edition, but seems practical enough), and (2) I'll assume that just as the Spelljammer in the helm can detect to some degree the nature of objects a near their vessel, they can also in some way determine the status of the air envelope. A perception roll seems simple enough a solution in that case.
I came to the same conclusion and Homebrewed my own spell. I used Detect Poison as a base, reduced the duration but increased the range.
https://www.dndbeyond.com/spells/1614826-detect-air-quality
Any creature inside a deadly air envelope that attempts to breathe will immediately discover that it can't. This means absolutely anyone can drive up next to something they want to investigate and send any creature into the adjacent envelope to check and report back. Exact methods for doing so will vary by access to minions and desired range, but e.g. you can use Find Familiar to do it very easily. Remember, Deadly Air can't hurt you with 30 seconds of exposure or less, so even a very fragile minion can check, and with a functional fly speed of your Intelligence score in grid spaces, even a basic Int 8 to Int 10 crew member will have a fly speed of 40-50 feet, which means it won't take all that long, and you don't need to get perfectly adjacent to the other envelope to check it. These envelopes are transparent, so you can signal the ship with body language (e.g. waving a flag) even before you report back to the ship, if you're the reporting minion.