why is this so overpowerd and yet underpowerd at the same time

This would murder so many prairie dogs.

teleporting to the other side of the fog allows you to keep it where you want it :)

When your all melee PCs go to run a train on a group of spell-casters with this and misty step. :D

It is 20ft radius, so the far side is at least 40ft away from you; most teleportation spells are either 30ft or wayyy more and cost a sizable spell slot . The spells area is also heavily obscured,  so you cannot see the other side, making targeting the far side of the cloud much easier as well.

You basically need to dimension door over there to achieve this. Otherwise, you could spend your movement going diagonally and then maybe be able to misty step *near* the opposite side, but this would probably take the dash action or disengage action to work reliably. 

I think this is a perfectly balanced spell.  It is easily defeated by a simple 2nd Level Gust of Wind spell - which any Wizard, Sorcerer, Druid, and some Clerics can learn.  I mean, shoot, even a 3rd level Triton character can cast Gust of Wind once a day innately. 

When you consider how many creatures have poison resistance/immunity, this spell becomes a lot less powerful. It functions like most AoE spells: meant to deal damage over a wide area to clean out the weaker enemies

I think the gust cantrip could clear this pretty well.

this + forcecage = op

It says a creature takes damage when it enters the area for the first time on a turn or starts its turn there. So does that mean a creature takes damage twice in a round if it is pushed in the area or the fog moves into it on the caster's turn? Or is that not what's intended?

Quote from DVision >>

I think the gust cantrip could clear this pretty well.

 Nope it would need to be the Gust of Wind spell. Nothing in the description of the Gust cantrip says that it could clear at 20 foot radius spell like this.

Quote from ArnoLamme >>

It says a creature takes damage when it enters the area for the first time on a turn or starts its turn there. So does that mean a creature takes damage twice in a round if it is pushed in the area or the fog moves into it on the caster's turn? Or is that not what's intended?

 In the scenario you have outlined it would take damage twice.

Quote from yellow_hat_elminster >>

Quote from ArnoLamme >>

It says a creature takes damage when it enters the area for the first time on a turn or starts its turn there. So does that mean a creature takes damage twice in a round if it is pushed in the area or the fog moves into it on the caster's turn? Or is that not what's intended?

 In the scenario you have outlined it would take damage twice.

 I think that it functions like moonbeam in damage, the creature only takes damage if they voluntarily enter it. Not sure though, if it happens, it's up to the DM in the end.

Quote from Barathol_Creed >>

It is 20ft radius, so the far side is at least 40ft away from you; most teleportation spells are either 30ft or wayyy more and cost a sizable spell slot . The spells area is also heavily obscured,  so you cannot see the other side, making targeting the far side of the cloud much easier as well.

You basically need to dimension door over there to achieve this. Otherwise, you could spend your movement going diagonally and then maybe be able to misty step *near* the opposite side, but this would probably take the dash action or disengage action to work reliably. 

 You misunderstand geometry.  With a 20ft radius circle, another point on the perimeter of the circle is AT MOST 40ft away from you, not at least 40ft away from you.

Unless the two points on the circle are 180 degrees apart, the distance between the two points will be less than 40 feet.  It's quite easy for two points on a circle to be less than 30 feet apart.

So does this "create a 20-foot-radius sphere of poisonous, yellow-green fog centered on a point you choose within range" ??? 

 or "The fog moves 10 feet away from you at the start of each of your turns, rolling along the surface of the ground" ?? which sounds like the spell is centered off you initially ???

yep. Also, the spell isn't very reliable outdoors.

Quote from gabrielrockman >>

 

 

 

Beyond 20

 

 

 

 

 

Quote from Barathol_Creed >>

It is 20ft radius, so the far side is at least 40ft away from you; most teleportation spells are either 30ft or wayyy more and cost a sizable spell slot . The spells area is also heavily obscured,  so you cannot see the other side, making targeting the far side of the cloud much easier as well.

You basically need to dimension door over there to achieve this. Otherwise, you could spend your movement going diagonally and then maybe be able to misty step *near* the opposite side, but this would probably take the dash action or disengage action to work reliably. 

 You misunderstand geometry.  With a 20ft radius circle, another point on the perimeter of the circle is AT MOST 40ft away from you, not at least 40ft away from you.

Unless the two points on the circle are 180 degrees apart, the distance between the two points will be less than 40 feet.  It's quite easy for two points on a circle to be less than 30 feet apart.

 They specifically mentioned the "far side", which I take to mean the other side of the Cloudkill sphere from where the caster is. Since the caster is unlikely to be right up on the perimeter of the sphere, the far side being at least 40 ft. away makes sense.

Quote from Vargussal69 >>

So does this "create a 20-foot-radius sphere of poisonous, yellow-green fog centered on a point you choose within range" ??? 

 or "The fog moves 10 feet away from you at the start of each of your turns, rolling along the surface of the ground" ?? which sounds like the spell is centered off you initially ???

This is how the spell works: You choose a point you can see within range (120 ft). The spell is cast in a 20-foot-radius sphere centered on that point. Now imagine a straight line extending out from you to the centre of that sphere (i.e. the point you chose when you cast the spell) and beyond, to infinity. At the start of each of your turns, the cloudkill moves 10 feet along that imaginary line, in the direction away from you. If you move during the spell's duration, that creates a new imaginary line between you and the centre of the sphere, along which the sphere will move away from you at the start of your turn.

If this is to over powered how do you all feel about fireball?  This is really quite underwhelming for the level, in my humble opinion. 

So, I have some questions about how this spell works with unconscious characters. Suppose, to pick a completely random and not-at-all-based-on-what-I-am-planning-for-my-next-session scenario, that Baba Lysaga wants to cast Cloudkill at the paladin who just took the jewel that animates her bestie—her animated hut. Let's also say for discussion purposes that the paladin has 8 hit points. Regardless of the outcome of the saving throw, the paladin will be knocked unconscious at the start of his turn in the cloud. On his next turn he must make a death saving throw, but if he is still inside the cloud:

1. Does he also have to make a Constitution saving throw for the ongoing damage?

2. Does the result of the saving throw matter whether he takes a failure on his death saves? Ie., if makes the Con save does he not take a failure? Pretty sure it doesn't work this way but I want to verify.

3. Assuming—again, completely hypothetically—that her turn is before his, he will only be in the cloud for two rounds due to its 10-foot movement and so I—err, she, Baba Lysaga— will have to send a scarecrow in to finish him off if he has made both of his other death saves, yes?

4. Of course, if she were in a hurry she could just finish him off with a dose of Magic Missile so she can get on with murdering bringing justice to the rest of the party. Does each missile cause a death save failure?