We travelled swiftly back to Rivendell, where we spoke with Elrond. He informed us that
This is the mark of a Gaunt-lord..perhaps you have seen one before? Sometimes Gaunt-lords use these sigils to summon the fell spirit that animates the wight.
‘The sigil you have brought is a mark of Drugoth the Black, a powerful Gaunt-lord. As for what drew the Nazgûl and this Gaunt-lord to Helegrod, I fear I now know what they seek….