The new Psi Warrior Fighter subclass has the feature Psionic Power which has the following option:
Psionic Strike. You can propel your weapons with psionic force. Once on each of your turns, immediately after you hit a target within 30 feet of you with an attack and deal damage to it with a weapon, you can expend one Psionic Energy die, rolling it and dealing force damage to the target equal to the number rolled plus your Intelligence modifier.
Is this ability affected by critical hits like a Paladin's Divine Smite or does it deal extra damage independent from the attack?
Best Answer
The damage die is not doubled
Critical hits double the damage dice on the respective attack. That means if an attack deals an additional ndx damage due to a feature that n becomes 2n.
The feature in question does not add the damage to the attack, however: It does not say "deals an extra psionic energy die of damage" neither does it say "rolling it and adding the value to the damage" but rather "rolling it and dealing damage". This indicates that the damage is not part of the attack and hence not doubled.
Another indicator is the templating which makes the extra damage contingent on dealing damage and not just on scoring a hit, implying that at the time the die is rolled, the determination of the attack damage is already completed.
The counter example is College of Swords Blade Flourish feature which triggers
and you can use the bardic inspiration dies
where the templating implies that the damage is extra damage of the attack and that the extra damage gets determined after the atatck roll rather than the damage roll.