Tributing a monster is a cost for “Spiritual Earth Art – Kurogane”.
You can Tribute a face-down EARTH monster for the cost of “Spiritual Earth Art – Kurogane”.
“Spiritual Earth Art – Kurogane” is an effect that targets 1 monster in your Graveyard. (So it will be negated by “Necrovalley” or “The End of Anubis”).