“Abanno” isn’t a widely recognized name for a mythical being in commonly documented mythology, so it may be a misspelling or a name used in a particular book, game, or local tradition.
One possible name you might mean is Abaddon. In the Bible, Abaddon is associated with destruction and the abyss; in some later traditions, the name is used for an angel or ruler of the abyss. But that is only a possibility—the words are not necessarily related.
If you tell me where you saw or heard “abanno” (or share the sentence or image), I can help identify the exact being.