Spontaneous Domain Casting
Source: Inner Sea Magic, p. 42
Replaces: This replaces the druid’s normal ability to spontaneously cast summon spells.
A tempest druid can channel stored spell energy into domain spells that she has not prepared ahead of time. She can “lose” a prepared spell in order to cast any domain spell of the same level or lower. This replaces the druid’s normal ability to spontaneously cast summon spells.