After watching the scenes resulting from the completion of the Sky Keep, we are back at the Sealed Temple. You honestly should think of going back to Skyloft and grabbing some Heart Potions (preferably with one upgrade on them), and grabbing the Hylian Shield from the Thunder Dragon.
Finish any preparations you have left, then go through the Gate of Time.
Temple of Hylia
Here, Impa will tell you to go through the doors of the temple to go outside (the doors facing the Gate of Time). Save the game with the Bird Statue first, then leave.
Outside, you’ll find Ghirahim at the bottom of the pit with Zelda, performing a ritualistic, freakish dance to summon back Demise. He’ll send up massive swarms of enemies to delay you.
The majority of these enemies are plain Bokoblin, which can be dealt with in one slice by now, but they come in swarms, so expect many spin attacks and Skyward Strikes.
Your goal is to simply continue down the path – however, I highly recommend actually defeating the enemies on the way, because you will be blocked at certain points, and no one wants hundreds of Bokoblin in their face, Master Sword or not.
The first of these blockades will have a group of weapon-wielding Bokoblin, numbering five or six. Defeat them and continue down. As you do, be careful of the Bomb-wielding Bokoblin – you’ll probably get hurt if you try to hit them with the Bombs in their hands, so wait until after the Bomb is gone, then deal some punishment.
The second blockade features three Moblins. You’ll pretty much be able to use the jump-over-the-shield thing I keep mentioning. Afterwards, continue down. As you do (yes, more enemies. Starting to love that Heart Medal?), you’ll find some more Bokoblin. In addition to the Bomb-wielders, you’ll find some with weapons.
The third blockade features a more-annoying blue Bokoblin. Defeat it and continue along the path. As you do, there will be some Bokoblin Leaders in the group. They can make the swarms impossibly more massive, thanks to their horn calls.
The fourth blockade features two Stalfos. You can take care of them, I’m sure. Just try to use spin attacks so as to deal with other Bokoblins. Further on down the path, you’ll end up fighting all types of Bokoblins, including the Archers, so keep your shield up (no bashing if you have the Hylian Shield).
At the bottom of the pit, Ghirahim, infuriated with your speed, will futilely summon a last wave of Bokoblin. Defeat them and you’ll soon fight Ghirahim.