Deflection Is the Default Answer
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Nine Sols is described by its publisher as a hand-drawn 2D action-platformer with Sekiro-inspired deflection focused combat. That single line sets the priority order for every fight.
Hold your ground and deflect
The official feature list opens with slash, deflect, charge into enemies and blow them up with the Taoist talisman. Deflection sits second in that list and in front of the payoff, which tells you where the fight is actually won. Backing away resets the exchange; deflecting converts it.
Charge in behind the deflection
Once an attack has been deflected, the charge is the described way to close the gap. That combination is the reason the game needs no block button in the traditional sense: the answer to pressure is a deflection that creates your own pressure.
Finish with the talisman
The Taoist talisman is the last item in the described sequence, which means it is a conversion rather than an opener. Spend it on an opening you earned with a deflection, not on an enemy standing at range.
Which answer to bring depends on the boss: see bow and talismans covering different gaps. Before you start the next hunt, run the checks for a new region.