What do you call a monarch with a title but no real authority?

Which word names both a combination of chemical elements and an enclosure of buildings? Which actress, a mother in real life, plays Grendel's mother in the 2007 film "Beowulf"? Who had a 2002 hit with "A Moment Like This"? Which monarch, who died in 1603, reputedly said "All my possessions for a moment of time"? A monoglot is a person who knows only one of what? Which southwestern river gives its name to a venomous lizard called a "monster"? A month after "The Bell Jar" was published in 1963, which poet took her own life? A month after winning the 1984 Olympic marathon, which runner married and added Samuelson to her name?