What it does
"Nitro-9" isn't a real Magic: The Gathering keyword or ability. It doesn't appear on any official cards, in the Comprehensive Rules, or in any set—including the Doctor Who Universes Beyond Commander decks, despite "Nitro-9" being Ace's homemade explosive from that series.
If you encountered this term, it may be a misremembered card name, a homebrew/custom card, or confusion with an actual mechanic. For explosive, damage-dealing effects in Commander, you might be thinking of keywords like "deathtouch," sacrifice-for-damage effects, or cards that deal direct damage when something dies.
If you can share where you saw "Nitro-9"—a specific card, set, or playgroup's custom format—I can clarify what's actually going on. Otherwise, I'd recommend double-checking the exact card name on Gatherer or Scryfall to find the real ability you're asking about.
Iconic cards with Nitro-9
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