What it does
"Thundara" isn't a real Magic: The Gathering keyword or ability—it doesn't appear on any official cards or in the comprehensive rules. It may be a misremembered name, a fan-made term, or confusion with another keyword.
If you're thinking of something similar, a few possibilities: you might mean Thunder effects (common in red lightning/storm flavor, but not a keyword), or perhaps a custom/Un-set card. There's also no mechanic by this name in any Commander-legal set.
If you can share where you saw "Thundara"—a specific card, set, or playgroup's homebrew—I can help clarify what's actually going on. For real keywords with similar flavor, look at Storm, Bloodthirst, or burn-related abilities, which I'm happy to break down instead.
