The new Rising Blade kata doesn't specify what bonus successes do. The opportunity option implies that they increase critical hit severity, but it isn't stated in the text. So do they increase damage, severity, both, or neither?

Looks like they don't do anything by default. The mention of them applying to the severity of the crit comes from the rule for Finishing Blow (p. 162: in case of Finishing Blow, bonus successes DO apply to the severity). And a double opportunity lets you forfeit this for a (usually) much bigger bonus - because if you're landing a Finishing Blow, it means your opponent's Strife just exceeded their Composure, so... ouch!

So basically it won't work against a heavily armored foe, but it is downright deadly in a duel against anything with 3 or less Resistance.

Unless you are a Kakita or somehow got to get in Striking as Fire on top of TN3, you are looking at Severity 5 crit pre-Fitness reduction. This technique is quite bad for not-Kakitas. It won't even end majority of the first blood duels, as chance of your opponent failing to get rid of a single severity are slim.

5 hours ago, Moribund said:

So do they increase damage, severity, both, or neither?

Currently they do nothing unless Rising Blow was used for a Finishing Blow.

5 hours ago, Franwax said:

So basically it won't work against a heavily armored foe, but it is downright deadly in a duel against anything with 3 or less Resistance.

Unless the heavily armored target is under the effect of Striking as Water for you or another.

Rising Blade seems to be designed on the idea that you are going to be using opportunities to boost it rather than bonus successes.

5 hours ago, WHW said:

Unless you are a Kakita or somehow got to get in Striking as Fire on top of TN3, you are looking at Severity 5 crit pre-Fitness reduction. This technique is quite bad for not-Kakitas. It won't even end majority of the first blood duels, as chance of your opponent failing to get rid of a single severity are slim.

Well it seems geared for finishing blows... and even a non Kakita will seriously augment the crit with a double opportunity (katana severity 5*2=10 + opponent's Strife which could easily be 6 to 12 at this point... yes, ouch)