I'm getting ready to play my Warlock and I'm already planning ahead on my invocations. Here is something I noticed, so tell me if I'm wrong or not. I was planing on picking up Voracious Dispelling as my first lesser invocation. This is dipel magic at will right? So if I find a magic trap with Detect Magic, can I take 20 on caster level check? The reason I ask is I can use it at will and there is no negative affects for failing, so taking 20 seems do able. This would give me a 26 for a caster check dispelling a spell from a 15th level caster. Am I missing somethin? This seems relativily powerful. Don't get me started on the fact that I can try and couterspell a caster like crazy. :)
I think that violates the spirit of the take 20 rule. First of, nowhere does it say that you can take 20 on a caster level check, because normally a person only gets a finite number of chances to dispel a given effect, and many times that's a single chance (like when countering a spell being cast).
In the end, it's up to your DM. If it were me, I'd probably treat it similar to disarming a trap via the disable device skill; I'd let you try multiple times, but each failure would increase your DC by +2. That way, you'd get to try more than once, but there is a penalty associated with failure.
According to the SRD all caster level checks are rolled on a 1d20, you cannot take 10 or 20 on a caster level check . . .
Flipping through the examples for traps in the DMG, I noticed that roughly 10-15% of those listed were magical traps. The remaining 85-90% are mechanical, with a wide variety of triggers ready to spring themselves on a hapless PC. Furthermore, casting detect magic could be a spell trigger itself, if only for sound or proximity. I don't think a Warlock on point duty would last very long without the Rogue's trapfinding ability, trapsense bonuses, plenty of class ranks in Search and Disable Device, and a good Reflex save.
Then again, if you had a Rogue sucessfully find a magical trap, determine that it was safe for you to approach and perform some magic without blowing everybody up, then sure. . . you could probably peek aorund and gingerly cast it a bunch of times until you were sucessful.
That brings up another question though. . . are magical traps considered items? I mean. . . are they dispelled, or just supressed for 1d4 rounds? I actually don't know, but the answer may save our character's lives. :)
There was a recent article on the D&D website about how to handle traps without a rogue, and magical traps were one area where a detect magic pretty much nullified the need for trapfinding. And, unsurprisingly, Dispel was a quick way to disable them.
As for how to handle such a thing, it depends on the trap. If it's a one shot trap, then the dispel would just get rid of it. If it's something that resets itself, then the dispel would disable it for 1d4 rounds or the length of time it takes to reset, whichever is longer.
And thanks for the snippet from the SRD. Good to know that's explicitly stated. I still think the +2 to the DC for each failure is a good way to handle dispel and magical traps.
I guess I worded my original post a little wrong. I didn't mean to imply that I was gonna take 20 on the roll. I was wondering that since I didn't see anywhere where a failed Dispel set off the trap, if I could sit there and keep trying. A Warlock only gets a set few of invocations so I was trying to figure out all the uses of the Dispel magic one. I am in a group that has no theif, so traps tend to be a problem for us. The high HP dwarf tends to be the default trap finder. If I can use detect magic and dispel magic to find the magic one it would be a great help. I'm gonna look for the article that Xellan pointed out and see what it says. Thanks for all your help.