Instructions
First Key
Fly left from the start of the "Ruins of Warfang" level to above the lower left dragon statue.
Fly to the first ledge and climb the vines to the very top.
Jump off the vines and fly right to the very last platform. Defeat the green monster there, which will cause two torches to appear. Light them with your fire breath and two more torches will appear on the vine-covered wall behind you.
Fly to the vines where the torches have appeared and light all four. This will cause a wall to lower near the first two torches. Fly back to the platform and cross to the other side of the wall to collect the first crystal key and head back to the first room.
Second Key
Fly to the area above the top left dragon statue. Climb under the first purple gate you see and pull the lever, causing the large key to lower.
Crawl back under the purple gate, climb the adjacent vines and latch onto the bottom ledge of the large key.
Use Spyro's lightning attack to activate the nearby switch, causing the above columns to push back.
Fly toward the columns, which will push the key until it fits inside the giant lock, lowering the nearby wall. Fly to where the wall has been lowered to collect the second crystal key, then return to the main room.
Third Key
Fly down to the platform near the lower-right dragon statue. Turn the wheel located on your right to lower a moving platform.
Pull the platform forward to the third rock, defeating all enemies along the way.
Switch to Cynder and use your "fear" ability on the tuning forks here, then quickly fly across the river and similarly activate the tuning forks on the other side.
Fly back to the other side and pick up the dropped orb. Place it on the switch. This will lower the wall and reveal the third crystal key. Collect it and return to the main room.
Fourth Key
Fly through the vortex to the upper-right dragon statue. Climb up the ledges on the left and climb the vines to the the lower section of the top.
Jump and use the wall-run ability to move to the next vine patch on your right and climb to the top.
Use Spyro's boulder-swing to break the wall, then climb across it while dodging the falling spikes. Drop down the platform on your right and defeat the enemies here.
Climb the next set of vines to the top of the ceiling and once again use Spyro's boulder attack to break the wall. Fight the last set of enemies and collect the fourth crystal key, ending the level.