Mad Alchemist feat question

[Kayoden Usoden]

I am helping make a character for a friend and I need some help. All I know about the “Mad Alchemist” feat is, it's in the PHB2, the description, and the perquisite for it. Can somebody please tell me what it does?

[its_all_ogre]

it does 3 separate things.
one increases damage using alchemist fire and similar, bit meh imo.
third enables you to create some difficult terrain by tearing open a tanglefoot bag, could be useful to control the battlefield.

second use is really quite powerful: you ready an action to throw a thunderstone at someone who is casting a spell or attacking.
if spell they must pass a will save vs your craft:alchemy check. as skills fly up quicker than saves this is good. if they fail they LOSE THEIR SPELL!
or throw it at an attacker and fort save or suffer -2 to all attacks.

i think this is fairly accurate.
so if you max ranks have artifice domain (+4 craft checks) and bung some other bonuses in there mwk tools etc, you can actually make a DRAGON fail to cast its spell! (i have an alchemist gnome in my group built in this way)