Bottom of the Valley
Right as the level begins, there is a grunt generator spitting out enemies on the wall to the left. Destroy that and you will notice some more enemies coming down the stairs. Walk up the stairs for a moment and destroy another generator, then go back down to the beginning, collecting the purple crystals and a cherry as well. As you come back to the beginning, there will be more grunts coming in from the right, across the bridge. Walk on over and destroy that generator as well.
Now that we have some room to breathe finally, at the beginning of the level where you started, there is a key on both your left and right, so make sure you grab those if need be. Walking downward, there is an archer standing still next to a chest; kill it and open the chest to find a potion. Grab the blue crystal next to the chest and open the barrel above the fire trap to find a speed power-up. Back on the other side of the bridge, there is a fire potion and a blue crystal, along with a pineapple hidden away in a barrel. For the perceptive, you may have noticed a runestone just floating down below in the river when you were fighting enemies or on the bridge. Climb the stairs on the right grabbing more purple crystals on the way and finding an apple at the top. To the right of the fire trap on the wall is a destructible wall with a hidden switch, white crystal, and a drumstick. Grab the items and flip the switch to raise the third runestone!
Middle of the Valley
After grabbing the runestone, continue up the valley to find some grunts coming down the stairs, along with a fire trap on the side of the wall. Kill the grunts, get around the trap safely, and then destroy the generator on the side of the wall. There is a key behind a fire trap, which you can easily walk around and grab, and there is a chest that contains some treasure. Walk up the stairs and you will notice a thunder hammer behind a red explosive barrel. First, kill off the approaching grunts and destroy their generator without destroying the red barrel, then grab the hammer as you'll need it in a second. Climb the stairs grabbing the purple crystals along the way, and there will be a chimera waiting for you. Use the hammer to do some damage to the chimera, and hopefully kill the bomb thrower in the process. After the chimera is dead, grab the spoils and the key at the top of the stairs if you haven't already. The chest on the left contains a cherry. The barrel contains the one and only hint scroll of this level.
If you have been following along, then there is no need to go back down as the scroll is referring to the runestone that we picked up moments before.
Top of the Valley
Avoiding the fire trap on the ground, climb the next flight of stairs and grab more purple crystals on the way up. There will be more grunts in this area and up the next flight of stairs up that are coming down to give you a beating. Kill off the grunts and destroy their generators. Nearby, there is some junk sitting next to the generator. Going downward, there is an empty barrel, a fire trap, a chest, and a blue crystal. Grab the blue crystal and open the chest to get some treasure. Climb up the stairs to find the exit with an explosive suicide grunt and a lone green crystal. Kill off the grunt and grab the crystal to finish off the level.