the point of the improved DC is so that the poison gradually gets stronger at a rate so that it is still possible for a secret vial to poison a high progression fortitude possesing opponent with a reasonable chance of success.

i suppose if the increase in DC could be based on the fortitude save of the crafter. the aim of this class feature is that a fighter or barbarian of the same level as the crafter would need to roll above a 10 before applying his fortitude. perhaps not a 10 because a spell caster of the same level still needs more of a chance than a natural 20. this is supposed to even the playing field for poison users who, at high levels, are only Barely effective against wizards/sorcerors with a low CON score. the secret vial also needs to craft all of his poisons weeks in advance, so he has to compete with the daily replenished skills of casting classes.

any help modifying this feature to be fair would be greaty appreciated.

and if anyone has any ideas for new poisonous talents (the current list is very short)

P.S. the use of INT modifier instead of WIS makes perfect sense, can you edit please Ali?