Druidic Elementalist (3.5e Alternate Class Feature)
From D&D Wiki
Some Druids choose to focus on the fundamental elements of nature instead of nature itself, gaining powerful casting abilities.
Replaces: Animal Companion, Wild Empathy, Resist Nature's Lure, Wild Shape
Benefit: Lvl 1 -- Elemental Attunement: Choose an element (Air, Earth, Water, Fire). You become attuned to your chosen element. All spells you cast with your attuned element's subtype ignore resistances and immunities. You can change your attunement through a 24 ritual during which you can cast no spells with elemental subtypes. (Replaces Animal Companion and Wild Empathy)
Lvl 4 -- Resist Elemental Force: You gain +4 on saving throws against spells, spell-like abilities, or other effects with elemental subtypes. (This replaces Resist Nature's Lure)
Lvl 5 -- Elemental Shape: You can become an elemental or para-elemental with HD equal to or less than your normal HD. You gain all traits/qualities, abilities and attributes of the elemental/para-elemental, but retain your own mental ability scores (Int, Wis, Cha). You can change shape no more than four times a day. (This replaces all other Wild Shape abilities for the Druid)