Plane Sailing
Astral Admin - Mwahahaha!
My way of handling it is as follows. The caster attacks with it by attempting to move it into a targets square, the spongy ball of fire always bounces back into the square it attacked from (or in the direction it attacked from if it jumped (two things can't occupy the same space) and a reflex save is made to avoid taking damage from the flaming sphere. The target doesn't move. In the 100ft high pillar example the flaming sphere would bounce off him and fall 100ft down the pit whether he saves or not, it can't co-exist with his space, not can it bull rush him out of it. It spongily bounces off and falls, possibly burning him in the process.
By the same token, I allow the flaming sphere to act as a burning obstacle, possibly blocking a corridor. Anyone can attempt to move past it, making a Ref save to avoid touching it and taking damage (or if they can clear 5ft height through some means, jumping right over it). Grapplers could attempt to wrestly each other into it, etc.
This all seems in keeping with the intention and basic description of the spell to me, and makes sense, so I'm happy with it.
Cheers
By the same token, I allow the flaming sphere to act as a burning obstacle, possibly blocking a corridor. Anyone can attempt to move past it, making a Ref save to avoid touching it and taking damage (or if they can clear 5ft height through some means, jumping right over it). Grapplers could attempt to wrestly each other into it, etc.
This all seems in keeping with the intention and basic description of the spell to me, and makes sense, so I'm happy with it.
Cheers