Trigger: You have an element gathered, and your next action has the Impulse trait.
You attempt to improve control of the channelled element you are about to use. Roll a Fortitude Save against your Kineticist Class DC.
Critical Success: Your Elemental Blasts gain +1 circumstance bonus on attack rolls and a damage bonus equal to your constitution modifier until the end of your next turn. Your Impulses with the Overflow trait gain a damage bonus equal to the number of damage dice rolled, and the DC to save against them increases by 2 until the end of your next turn.
Success: Your Elemental Blasts gain +1 circumstance bonus on attack rolls and a damage bonus equal to your constitution modifier until the start of your next turn. Your Impulses with the Overflow trait gain a damage bonus equal to the number of damage dice rolled, and the DC to save against them increases by 2 until the start of your next turn.
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Right now, the Kinecitist has 4 reaction options: Deconstruct Element, Air Cusion, Shield Block (with Stone Shield), Deflecting Wave. Only one of those is not tied to a specific element. So I thought why not add an option to increase the damage with one? The overall impression is that the damage is lacking, and the action economy is already pretty tight.
Math - Overall, the reaction has a 60% chance of success, including 10% critical success chance. The only exception are levels 7,8,15,16, when the Class DC and Fort Save expertise improve. At these levels, the chance actually improves to 70/20% chance to succeed/crit succeed.