The Alder Spirit

The Alder Spirit was associated to goddesses of fire, forge, smithcraft (wordsmith) and housecrafts (home and hearth witchery or domestic witchcraft). The word Elder is derived from an old Anglo-Saxon word aeld meaning fire.

Celtic Goddess Brigid, The Lady of the Hearth (Fire), whose name means "Bright Arrow" (very much like the Druidic Animal associated to the Alder Tree, the fire-red Fox, whose body moves like a pointed arrow when hunting).
Alder elements are water and fire (the alder wood becomes stronger and harder when immersed in water, and the charcoal was used in the forges for smithcraft and in the ovens for witchcraft).
Brigid is a goddess of fire and water. Also Cerridwen (her name is derived from the Celtic word cerru meaning cauldron which like the Goddess herself, symbolizes the transformative power of magic, wisdom, rebirth and creative inspiration, and the adjective (g)wen meaning fair, beloved, blessed or sacred, and sometimes suffixed to female names) as a cauldron-goddess, is very well represented by the Alder Spirit. Cerridwen, The Magician, is the Keeper of the Cauldron of Sacred Knowledge (Ancient Lore) and (Poetic) Inspiration from the otherworld; spirit world; fae. And know that Circe had her island surrounded by a magic circle of alder trees.

Ceridwen by Christopher Williams (1910)

The Magic Circle by John William Waterhouse (1886)

Cerridwen's Cauldron by Emily Balivet (2009)

- Source:
http://www.mysticfamiliar.com/library/treelore/alder.html
http://www.goddess-guide.com/ceridwen.html