Few weapon fighting question (regaldless critical)

[andbr22]

Does Kenasai III signature weapon stack with Improved critical?
(I dont think so but i wan't to be sure).

If you roll is in critical range (like you roll 18 with a rapier) does it mean you always hit monster? (even when enemy is immune to critical hits, or have so high AC you cannot even dream to confirm critical).

[Sinni]

yes it stacks, but after imp crit

to keep your rapier example:
rapier without anything: 18-20
rapier kensai III: 17-20
rapier with imp crit puncturing: 15-20
rapiier kensai III with imp crit puncturing: 14-20 (and not 13-20)

no, only a natural (=rolled) 20 is a guaranteed hit

[k1ngp1n]

yes it stacks, but after imp crit

to keep your rapier example:
rapier without anything: 18-20
rapier kensai III: 17-20
rapier with imp crit puncturing: 15-20
rapiier kensai III with imp crit puncturing: 14-20 (and not 13-20)

no, only a natural (=rolled) 20 is a guaranteed hit

What he said.