I break the rules.How do you handle this narratively?
I'm talking about creatures like ghosts and fire elementals.
In my games I describe it as the creatures having a sort of energy core that can be disrupted.
Visually I think of the creatures that are fought at the end of season 3 of Legion.
This is how my group looks at it to. Things that lack a solid form still have to keep themselves intact. Most physical things don't affect them much, but magic tends to draw out more of the essence (assuming they have resistance).Fire elementals don't have an organic structure, but they do still have some cohesive form, and if that form is disrupted involuntarily, it can cause them to lose a small piece of themselves, becoming diminished as a result. Magical weapons cause a greater disruption.
In D&Dese, making an object float through the air is a spell-like ability. In this case: mage hand.If a ghost can pick up an object and make it float through the air, or an elemental can open a door, then why wouldn't a physical object be able to strike them?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.