I've always loved JRPG's incorporation of summonable creatures to use in battle (ie: "Tales of" series, "Final Fantasy") and wanted to create some of my own. Plus animals have always been my love and focus.
Idea for this elemental was actually the first I came up with. Its spines react to lighting around it and will stand up as flexible quills, creating a bristling look. The horn on its head acts as lightning rod that absorbs the energy for later use via a thunderous roar or lightning breath in place of traditional fire.