make 15 feet diameter ring that just surrounds you safely, and make it damage anything outside.

Do you still do a DEX save if you enter or pass through the wall or just straight 5d8 damage?

Have the bbeg use this to lock the PCs in a space with him

I fell into a burning ring of fire
I went down, down, down and the flames went higher
And it burns, burns, burns, the ring of fire
The ring of fire

How much light comes off a WoF?? I never really thought about this question before until it came up in our game, when our wizard cast WoF inside a darkness spell.. its magical fire so I would think it sheds light, 4th level spell...does it cancel out the darkness????.. our DM ruled it just glowed dimly in the darkness but didn't cancel it out. our table was cool with that, but I was wondering what everyone else's thoughts on it were.

Does anyone know if this blocks line of sight? It's not really clear if its a wall of solid fire (almost like lava), or a wall of loosely contained fire (like you'd see above a large bonfire), just curious :)

Quote from Tigerboy007 >>

Does anyone know if this blocks line of sight? It's not really clear if its a wall of solid fire (almost like lava), or a wall of loosely contained fire (like you'd see above a large bonfire), just curious :)

 The spell states that the wall is opaque, so you cannot see through it.

So: 

Choice 1) position a target so the wall intersects their position, they get a saving throw when the wall appears and can move out of the wall to the safe side (if they want!) on their turn and suffer no more damage

Choice 2) position a target inside the wall, the target gets no saving throw and can either move through the wall and take damage no saving throw to escape, or stay where they are and take damage no save

Tactical creatures: send in creatures with fire immunities into the wall and have them take the dodge action (or attack), they can block PCs from leaving the area

Nowhere in the PH or the DMG does it say that. An object is not immune to fire damage unless the description says it is. Whether something that takes fire damage continues to burn is up to the DM, but IMO it would be a little absurd to rule that "produce flame" can't light a campfire or that "fireball" can burn a humanoid to death in an instant but leaves the loose papers next to them untouched.

Quote from Amaraiel >>

I want to cast a circle wall around a group of enemies and roast them alive

 "And then maybe later play some D&D."

If you're running an encounter with a pit fiend, have them cast this spell, centered on themselves. Any melee attackers will be taking 5d8 fire damage per turn, and if they try to run, they'll have to suffer an opportunity attack.

I would assume so

Define 'solid surface'...

...a dragon is pretty big, from next to tail-tip. Is its back a 'solid surface'? Could you cast wall of fire down the spine of a dragon? Or are we talking 'surface' such as a floor, wall, 'rigid surface', etc?

Quote from Trowzers >>

The rules here don't specify whether Wall of fire can set objects on fire. Can it?

 If the object is flammable, I would think so.  

If you placed one down a hallway, would something take damage each step as it proceeds down the wall, traveling along the wall, and not from one side to another?  I feel like it would.

This stands for fireballs and lightning bolts under water. Nothing chnages because there is no clause in the spell for that. Fireball rolls full damage underwater, lightning bolt doesnt get extra area or extra damage.

 

Fireball might roll full damage when cast underwater but any creature fully immersed in water has resistance to fire damage per the PHB Ch. 9 - Underwater Combat.

Quote from Kalakoi >>

This stands for fireballs and lightning bolts under water. Nothing chnages because there is no clause in the spell for that. Fireball rolls full damage underwater, lightning bolt doesnt get extra area or extra damage.

 

Fireball might roll full damage when cast underwater but any creature fully immersed in water has resistance to fire damage per the PHB Ch. 9 - Underwater Combat.

 I am aware. My response answered several questions, and no questions were "how does fire damage work with bodies of water?"

Can you see through a Wall of Fire?

can you see through normal fire?

what if you cast this on a wall? would the flames affect for the entire 20 feet as a width?