I was playing DnD 5e earlier today and one of my party members cast gaseous form upon itself and then got into a fight. While we know that the party member is currently protected from most forms of attack, magical attacks would still hit. What couldn't be determined was the AC of the party member in gaseous form. So my question is: should the creature's AC remain the same even in gaseous form or should it change?
Gaseous form does not change your armor class.
A spell’s description tells you its effects, as we see in the rules for casting a spell:
Each spell description in Chapter 11 begins with a block of information, including the spell’s name, level, school of magic, casting time, range, components, and duration. The rest of a spell entry describes the spell’s effect.
Since the description of gaseous form doesn’t mention armor class, your armor class is unchanged.
1\$\begingroup\$ This answer could be improved by explaining whether the AC effect of things such as magic armor or devices of protection still apply, as per Dale M's answer at the suspected duplicate. Another option would be to copy your answer to that question. \$\endgroup\$– KirtOct 9, 2022 at 22:48