pf2e.fyi
From Pathfinder Rage of Elements, which isn't enabled.

Improved Elemental Blast

FEAT 8
ARCHETYPE
Archetype Kineticist
Prerequisites Kineticist Dedication

The power of your elemental blast improves. The damage of your elemental blast increases by one die.

Special You can take Improved Elemental Blast a second time at 14th level to increase your Elemental Blast to three damage die, and a third time at 18th level to increase your Elemental Blast to four damage die.
Pathfinder Rage of ElementsOGL