You're going to have to square off against no less than two Invaders in the Aldia's Keep section of Dark Souls 2. We'll help prepare you for these fights, and show you how to get hold of some tasty loot without ruining all of that armour you've carefully collected.
Aldia's Keep guide
Make your way back to the Ruined Fork Road bonfire in the Shaded Woods region of the game. Now take the middle door, and follow the path until you come across a Red Tearstone ring in the pond. Carry on down the path and go through the big door at the end of it using your King's Ring. Just make sure you have it equipped to get this door to Aldia's Keep open.
Grab the Petrified Dragon Bone and the Soul of a Nameless Soldier from the tree on your left, then take the Alluring Skull and Poison Throwing Knife from just further along. Kill all of the enemies that attack you, then go into the building up ahead and light the bonfire. Make your way back outside, then head towards the left-hand side of the bigger building ahead of you. Give the coffer here a good whacking to loot a Dark Mask and a Sunset Staff.
Now go and grab the Fire Seed that's just to the right of the stairs over on the far side from where you are now. Once you've picked it up, go up the first two sets of stairs and take the Radiant Lifegem from the little pond just in the middle. Now go up the next set of stairs and head over to the far left-hand side to get a Twilight Herb.
Aslatiel of Mirrah
Make your way through the next passageway, but be ready to kill a new Invader called Aslatiel of Mirrah. Now go through the door at the end of the hallway and take the Fading Soul from the middle of this new room - move forward quickly after grabbing it though, so you avoid the worst of the bone dragon's attack.
"Walk up to each mirror in turn, and back away as soon as you've engaged the enemy to make life a little easier on yourself."
Go back towards the entrance to loot a Darknight Stone, then enter the hall beneath the stairs and go all the way around the corner to your left. Activate the lever you come to, then go back over to the opposite side and talk to Royal Sorcerer Navlaan. Take a moment here to browse through the store and stock up on any essential items.
Make your way back to the main room and go up the stairs on your right. Walk around the corner to your right and take the Great Magic Barrier from the coffer you find. Now head back the way you came and kill the trio of enemies within the mirrors. Walk up to each mirror in turn, and back away as soon as you've engaged the enemy to make life a little easier on yourself.
Grab the Petrified Dragon Bone and Northern Ritual Band +2 from the end of the hallway, then go back to the main stairs and head over to the far left until you come to a new staircase. Go all the way up it and step out into the new hallway above. If you head all the way over to the right and walk down the hallway, you'll eventually come to a coffer that contains a pair of Bonfrie Ascetics.
Killing caged enemies
Head back into the main room, then grab the Crimson Water from next to the cage. Kill the massive frog held captive inside, then go through the door at the end and keep walking until you come to a lever on a statue. Pull it to open up a new door, use a Pharros' Lockstone on the face over in the corner, and then carry on walking down the hall.
If you attack the painting that's just on your left, you'll expose an enemy. Kill it, then use a ranged attack to take down the enemy hanging in the cage above you. Grab the Radiant Lifegem nearby, then keep heading down the hallway and through the next door along.
After entering the new room, take the stairs all the way down, and use ranged attacks to kill any caged enemies. If you don't have any ranged weaponry at this point, take all of your armour off, open the gate, and simply draw the enemies outside. If you fight in the acidic waters of the pool, you'll only ruin your armour.
When all of the enemies are dead, head into the poisonous water to get hold of a Large Soul of a Nameless Soldier, four Corrosive Urns, the Aldia Key, a Soul Geyser, and a Petrified Dragon Bone. Go back out and head up the stairs (with your armour back on!), then take the door on your left. Hit the nearby painting to expose another enemy, kill it, then carry on down the hallway until you come to a door on your right.
"Watch out for [Royal Sorcerer Navlaan]'s deadly magical damage which packs a mean punch and can travel quite some distance."
Kill the pair of enemies in this new room, then grab the Soul of a Proud Knight. Make your way towards the cage over at the other end of the room, kill the enemy, then grab the Large Soul of a Brave Knight from the far wall. Turn around and go through the door on your right. Whack the enemy in this new room to make a hole in the wall, then kill it. Finish off the caged bird ahead of you, then enter the room on your right.
Turn round and go back through the damaged wall. Pass through the doors ahead of you, then grab the Twilight Herb and Simpleton's Spice items over on your left. Be ready to dodge back from the ambushing enemy as soon as you've done so.
Royal Sorcerer Navlaan
Once the enemy is dead, go through the newly-created hole in the wall to take on the Invader called Royal Sorcerer Navlaan. Just watch out for this creature's deadly magical damage which packs a mean punch and can travel quite some distance. As soon as you've finished the fight, go over the bridge and then through the misty door to start the fight against the Guardian Dragon.