Tempest
If you were looking for the Eldar tank, see Tempest Tank
Tempests are vaguely humanoid living storm clouds from AD&D. They are listed as "Composite Elementals", meaning they are a mix of all four elements.
Tempests are extremely territorial and take any entry into their airspace as a direct challenge. The have a whole host of wind, rain, and lightning spells and powers at their disposal, including wind wall, gust of wind, lightning bolt, and chill touch.
In 5th Edition, thye got retconned as the Elder Elemental of Air. Now renamed Elder Tempests, they look like giant feathered winged serpents.