What level should this spell be (3.5)

[Zaydos]

I thought up this spell and wasn't sure what level the spell should be. Also I want it to have a thematically appropriate (inexpensive) material component but couldn't decide what.

Chaos Sphere
Conjuration [Chaotic]
Level: Sor/Wiz 5
Components: V, S, M?
Casting Time: 1 standard action
Range: Medium (100-ft +10-ft/level)
Area: 20-ft burst.
Duration: 1 round/level.
Saving Throw: Fortitude partial.
Spell Resistance: Yes

You summon forth a blob of roiling chaos stuff filling a 20-ft radius burst at the location you designate. It ignores gravity floating where you summon it and dealing 1d6 damage/2 caster levels (max 10d6) to all creatures within it when it is summoned. At the start of each of their turns they take an additional 1d6 damage/4 caster levels (max 5d6) as long as they are within the swirling chaos stuff and have all movement modes reduced to 5-ft while within it. A successful Fortitude save halves the initial damage and the damage taken afterwards as well as negating the reduction to speed.
The chaos stuff provides partial concealment to all creatures within, but also obscures vision giving all creatures partial concealment against them.

Material Component: Suggestions please?

So what level should that be? Thank you all in advance.

[DracoDei]

Well, it is like a Quickened Fireball and an Acid Fog (or whatever the one that does damage while limiting movement is... or is there one of those?)... of course, since it is a set pair, and uses a single save, it probably isn't as good... but Evasion and Improved Evasion don't help against it, and Mettle is much rarer, and only negates a fairly minimal effect (since they would leave the area ASAP if they made their save anyway)...so that is a good place to start in figuring out the level. At least 5th I think. Might be back later to offer more thought out input.

[peacenlove]

Freezing fog (6th level) from spell compendium is similar to this spell but
1) deals less damage
2) Lasts longer
3) Has no SR and no material components
4) Is generally stronger and restricts targets more than your spell

So i would place it as a strong 5th level spell