Killing Ultimate Chameleons

[Kylas]

So I'm having to 2 separate issues but similar issues.

1st in the campaign that I run The are 2 players who are playing twins that have taken the chameleon Prestige class. I thought the build was interesting at beginning levels but now we are approaching level 15 and I find myself stretching a little to challenge them. They both are playing the ultimate Chameleon build. Its a mixture of monk/iajutsu master/chameleon levels. With an unbuffed non armored 30 AC minimum touch AC 27. And this double caster level ability of the chameleon is crazy.
Yes I know I created a monster but I do like the PC's flavor in game and the campaign is pretty high powered, but these 2 players always seem to be able to get out of any jam with ease.
Im not trying to kill them but I just want a few tips on spells or magic Items, tactics to use against them. I'd like to stick to the PHB and DMG if possible but PHB2,Spell Compendium and MIC are OK.

2nd problem has to do with a campaign I'm in. The DM has announced that there will be PvP in his campaign and one of the players is going to play.... Chameleon. ANy suggestions for 1v1 battles. Same resources.

Thanks!

 

[Shin Okada]

I don't see why AC 30 is that much problematic. At level 15, that AC is quite normal even for casters when you are using various splat-books. In my current 15th-level campaign, PCs who are using armor and shield, including a cleric and a multi-classed warmage, all have unbuffed AC of med-30th and some of them have nearly 30 touch AC. The Sorceress/Ruathar/Abjurant Champion likely to have the lowest unbuffed AC but she usually have her AC +9 Shield spell always on when she awake. And as a DM I have to expect that both Haste and Recitation will be used in the first round of somewhat important fight (two characters can cast Haste and two characters can cast Recitation). That will give them additional +3 AC and +2 save at least. The warmage even has a ring of evasion.

AC 30 is well within reach of melee attacks which creatures and NPCs of appropriate CR do. Evasion is a strong ability but still fail from time to time. And at level 15 or so, there are tons of Fort/Will save or even non-save damaging spells.

Chameleon is a strong class. But their highest-level spells are of 6th-level even though dedicated spellcasters of their level are wielding 7th or 8th level spells already. And their HPs should not be that much particularly high.

I don't see much problem on those builds.