Celestial Storm

Skill. A celestial storm forms at target foe's location for 15 seconds. All foes in the area take 40 damage each second.

Skill. Deals 40 damage each second (15 seconds). Also hits foes in the area of target's initial location.

[edit] Acquisition

This skill is temporarily acquired by primary elementalists by talking to Kuunavang in Raisu Palace, Imperial Sanctum or Raisu Palace (explorable area).

This skill only recharges after morale boosts.
The skill actually strikes for 40 damage four times every second, in effect striking for 160 damage per second. Additionally, the skill description suggests that the damage is armor ignoring, when, in fact, it is reduced by armor. Exactly 1 pulse per second inflicts Lightning damage, exactly 1 pulse per second inflicts Cold damage, and some of the pulses inflict Fire damage, the other pulses inflict unknown types of Elemental damage, presumably Earth damage.
Consider Echo chaining this skill to quickly dispatch foes (including Shiro).