I’m confused when it comes to the high ground combat modifier and fly or spider climb effects. Its clear that any ranged attack does not gain a high ground bonus. But just what exactly gives you high ground? A couple inches or feet?
At what height would you need to be in order to gain high ground while flying? One of my players often hovers or moves just above the ground. Is this sufficient for the bonus?
If you were on a wall using spider climb, could/would you gain it?
Since charge can be used while flying, if you charged down to an enemy do you gain it?
When you are larger than an opponent would you gain it, for example a large creature attacking a medium?
I would argue that Tim’s answer is not accurate. I understand that his proposed solution is not based on raw, but it is based on the idea that “your opponent must fight gravity to advance”.
That it is just not the case for this rule. Higher ground advantage does not seem to emanate from a difficulty your opponent has, this is already covered on a separated rule for fighting uphill. It seems to come from an ease to strike from having gravity aid you. Swinging down is easier than swinging up.
This is further evidenced by the rule on Combat while Mounted that specifically determines you get high ground bonus while mounted if your target is smaller than your mount.
It is still up to the GM to call what high ground is, I would recommend simply giving higher ground advantage to any creature who is at least 5 foot higher than another.