does a wizard specialized in counterspelling really work, or the cost of it doesn't worth ?
i ask because my DM often put us really buffed NPC to fight..
Honestly a sorcerer would be better at specializing into counterspelling. At least with using dispel magic/greater dispel magic. You use two spells known and you can effectively use all your spell slots to counterspell as necessary. A wizard would need to know how many spells to prepare in advance for dispel purposes...at which point you might as well have played a sorcerer if you're going to prepare most of your spells for dispels.
However, the best answer is arcanist. If I recall correctly they get some nifty arcane study abilities (or whatever they're called) that help with counterspelling and they can know any number of spells and prepare a group for use that day, but then casts from that group as a sorcerer. Best of both worlds.
as a sorcerer what are the best to pick?
I don't even really know how counterspell works.. as i sorcerer i can counterspell everything using the few spell i know?
To counterspell you've to ready an appropriate action. After this you have to pass a Spellcraft check to identify the spell. If you pass it you can either cast the same spell and automatically deny the effect of the enemy caster, or cast Dispel magic and make a caster level check. If you succeed this check your enemy's spell is denied. If you take the Improve Counterspell feat you can automatically deny a spell casted by an enemy caster casting a spell which is of the same school of the one he is casting, but it has to be one or more level higher.
That said as a Wizard you could try to pick the Counterspell specialization school, it's good but Counterspell Mastery is available very few time a day. To save actions you could take an improved familiar (like an Imp/Quasit/Mephit) and let him use scrolls or wands of dispel magic as a readied action.
As a sorcerer I'd pick the Arcane Bloodline.
As Pandamonium notes you can counterspell a spell using only the same exact spell, except if you use the spell Dispel Magic. It funciton against any spell, but requires a caster level check to succeed. Greater Dispel Magic simply gives you a +4 bonus to counterspell (that is the main difference between it and Dispel magic). The reason counterspelling normally isn't popular is because you have to have the same exact spell ready to counter it. Having the Improved Counterspell feat enable you to use the same school of spell. The bonus here being that you automatically succeed if it's the right school and at least one spell level above.
For sorcerers the limited amount of spells known isn't a drawback because you only need to learn Dispel Magic and Greater Dispel Magic. A wizard is more limited because he doesn't know which spells he's going to have to try to counter or how many times per day he will want to do it. So he has no idea how to best prepare his spell slots. As a sorcerer you don't have to prepare, you always have you spell slots available to counter if you know Dispel Magic. And if you pick up the feat Improved Counterspell and learn a wide array of spells from different school you're likely to have a greater level of success in counterspelling.
Also, on enemies that start the fight buffed Dispel Magic will work to strip their buffs, as opposed to doing nothing if you attempt to counterspell. You can't counterspell what's already been cast before the fight starts.
thank you.,..now it seems more clear to me :)
so counterspell works when someone is casting his buff :)
but with dispel magic, all buffs on the NPC will be destroyed or one/use dispel
thank you all for making this clear to me!
The counterspell specialist wizard gains the ability to counterspell as an immediate action at level 6. Very nice for this build.
Also concider destructive dipel to make dispell magic even better.
To clarify, the immediate action dispel is:
Counterspell Mastery (Su): At 6th level, you gain Improved Counterspell as a bonus feat. You may attempt to counterspell an opponent's spell once per day as an immediate action (instead of a readied action). You must use a spell at least one level higher than the spell being countered to use this ability. You can use this ability once per day at 6th level, plus one additional time per day for every 4 levels beyond 6th.
So, it only works once per day at 6th level, to a maximum 4 times per day at 18th level. In my opinion, it's just not enough times per day to make it useful. But it depends on how often you're GM is actually having opponents cast spells in combat.