Why does Nashandra only appear when you have the Giant's Kinship?

Question

In Dark Souls 2, in order to fight Nashandra you need to possess the Giant's Kinship which you get from the Giant Lord in Memory of Jeigh.

This got me wondering: "Why do you need the Giant's Kinship to fight her?"

The item's description reads:

Each king has his rightful throne. And when he sits upon it, he sees what he chooses to see.

Or perhaps, it is the throne, which shows the king only what he wants.

Which doesn't give any clue on why you'd need it.

Now, what I do know is that Nashandra craves power. And that she waits for the Bearer of the Curse at the Throne of Want after they obtain the Giant's Kinship.

Now, when talking to Shannalot before going to the Throne of Want, she says:

If you proceed, Nashandra will come after you.
Knowing that you will take the throne, and link the fire.
She covets the First Flame, and the Great Soul.

Does this mean that the Giant's Kinship commands the Golems? And with that, that Nashandra let you do all the dirty work so that she could take it from you and therefore take the throne for herself?

Answer 1

What the Giant's Kinship actually does (activate the Golems? Open the Throne?) is a bit of a mystery, but what we do know is that you can't access the throne without it.

Along the way, she tries to direct you a bit. When you talk to her after gaining the King's Ring she says:

Brave Undead, seek the throne. Follow the symbol of the monarch, and do what must be done.

After you meet the Ancient Dragon, then go back and speak with her again:

Brave Undead, what did that dragon tell you? That thing is a prop, a false deity. Don't be fooled, my Undead.

If you go back and visit her after you gain the Ashen Mist Heart, she says:

Seek the forest, you, where those wretched Giants slumber.

She leads you on to try and gain the Giant's Kinship. She knows you need it to gain access to the throne.

WARNING - SPECUALTION AHEAD. PLEASE TAKE CARE
I feel that Nashandra is attempting to pull your strings through the entire game, making you feel as though she wants you to become the new King of Drangleic. However, shock! Horror! She was playing you all along!
It's pretty obvious we can see that happening once we've beaten the game once round already.
END OF SPECULATION ZONE. TAKE CARE AND HAVE A NICE DAY

Basically, the reason that she leads you on (so horribly) is that either she can't or won't get these things herself, (most likely can't, because Vendrick hints that he attempted to seal the way from Nashandra, and the Ancient Dragon seems to know a thing or two about her true nature as well) so she gets you to do all the heavy lifting, then attempts to snatch the victory from your hands, just when you were so close!