Use King of the Swamp depending on what you need. You can send it to the Graveyard to get Polymerization or use it as a Fusion Substitue. It's recommended to have more copies of this card and replace other Fusion Substitute monsters.
Umm... Why is shaman summoning a monster from his own graveyard when it clearly states in the text the opponents graveyard?!?! Wtf?!?! There are so many rules in this game that don't make any sense. Its irritating... Very irritating.