Bottom of the Armory
Begin the level by standing still and waiting for an explosive suicide grunt to come your way, and then destroy the red explosive barrel nearby before the grunt gets close to you. Walk past the destroyed barrel and try shooting the general up ahead from a distance. Kill the general and grab the key it drops, then walk up to where the general was and then kill the archer. Destroy the wall with the swords to reveal a hidden room with an apple inside. Walk toward the chest near the boiling pot, and then take care of another archer and a generator in the corner that is blocking a yellow crystal. Grab the crystal and then open the chest for a banana bunch. Walk below the pot and grab the blue potion nearby. Deal with two anklebiter generators and a grunt generator near the potion, and then open the barrel on the path for a speed power-up. Destroy another generator past the barrel, and then climb the stairs with the blue crystals. Get off the stairs on the right with the floor spike trap and door, then destroy the door to open a small hidden room with a green crystal inside.
Walk to the top of the left side to find the first hint scroll.
Just like the Mountain Kingdom, there will be detours you can take that will take you to areas around the level without needing to waste keys. With that said, ignore the locked gate in front of you and take care of all the enemies and generators on the left of the gate. Open the barrel for some levitation wings and the chest for a drumstick. Walk to the left and over the floor blade trap to find a keyring and a green crystal near another generator. Walk back to where you opened the chest and head right to find a split path with an anklebiter generator just above. You can't go down as the path is blocked, instead, go past the anklebiter generator that you destroyed and keep following until the path turns next to a blue crystal in the corner. Destroy a generator past the floor spike trap, and then grab the keyring next to it. Keep walking on the path and you'll reach a set of stairs with some blue crystals on it.
At the top of the stairs is a number of grunts along with a bomb thrower and archer. DO NOT OPEN THE TOP MOST CHEST NEAR THE GENERATOR! You will see why in just a little bit. First, kill the bomb thrower and archer, then deal with all the grunts, anklebiters, and their generators. Now that there aren't any more enemies around to harass you, we can open the chests and barrels in peace. The first barrel at the top of the stairs has some treasure in it. The chest to the right of the barrel has some ham. BEFORE OPENING THE CHEST AT THE TOP, OPEN THE CHEST DOWN BELOW FIRST! The chest down below will contain a halo, which I think you will know where this is going. Now, open the chest at the top to reveal a black death. Steal some EXP from that death through the halo, then grab the key next to the boiling pot. Open the chest above the boiling pot for a cherry, then grab the blue crystal up top near a green toxic barrel. Grab a cherry next to another green toxic barrel, then head on down the stairs near a previously destroyed generator for a keyring.
Walk back up the stairs and open the locked gate that has some grunts behind it waiting to get to you. Destroy the generator up top near a chest, and then destroy another three generators down a set of stairs of blue crystals and around the corner. Grab the yellow crystal and then head back to that chest from earlier. Ignore the chest as it has a bomb inside, but get the blue crystal on the other side, a 3-way shot power-up in a barrel and some treasure inside a chest. Now go back to where you grabbed the yellow crystal down below, and walk up the set of stairs with a turbo power-up on it. Grab the power-up and then destroy the anklebiter generator up here. Open the barrel next to the switch for some treasure, then pull the switch to raise a platform in the room over for a keyring. Grab an apple in the corner and then backtrack to the other side to grab the keyring. With all the backtracking, you may have noticed a switch on the floor that makes the floor re-appear as long as you stand on it. Because it needs someone to stand on it, or someone/something to be in the middle of the floor while it's on, just ignore it and instead take the other path in front of the stairs with the turbo power-up to get to that area.
Getting the Runestone
Open the chest next to the locked gate for a lightning amulet. Destroy the anklebiter generator down below, and then open the chest next to it for a potion. Grab the green crystal, then head right to deal with some grunts and two generators. Grab the blue crystal in the corner, then follow the path that has a floor spike trap with some grunts coming down. Destroy a generator dead ahead, and then grab a green crystal to the left and destroy another generator. Go back and this time go to the right to find a locked gate, with some grunts on the other side. Kill the grunts and their generator, grab the black crystal, then pull the switch that will lower a wall somewhere with a golem inside. Backtrack to the area with the floor switches and the invisible floor, but this time go up to where two anklebiter generators are, one on the path, and one next to a locked gate that we didn't go through to avoid wasting a key. Look familiar? That switch just moments before lowered this wall. Open the barrel next to the wall for a hint scroll.
We'll see what that means soon, for now, deal with the golem inside. Kill the golem for a keyring, and then flip the switch that the golem was guarding to raise a platform near the boiling pots with a Runestone on it! Before going back, shoot the wall underneath the staircase to reveal a small hidden alcove with a golden icon inside, which was what the scroll was referring to. Now, backtrack to this boiling pot area and grab the fourth Runestone!
Top of the Armory
Head back to where you flipped the switch to lower the wall with the golem, but on the left path where you grabbed the green crystal. Continue on while avoiding traps, and deal with the grunts, anklebiters, and the generators on the other side of the wall by throwing a potion or using the turbo attack.
Walk to the end of the path to find a green crystal and what appears to be a dead end. Destroy the wall in front of the floor spike trap to reveal a hidden room with some treasure. Grab the treasure and then destroy the cracked wall on the left to continue forward. Kill off some grunts and their generator, then open the chest in front of the wall nearby for a potion. Walk down below where you used the turbo attack or a potion on the enemies, and grab the yellow crystal in the corner. Walk up the stairs of blue crystals and then take of some grunts and a generator midway. Keep walking up some more stairs and then take care of one last generator at the top, next to a hint scroll.
By following this guide, you should have already collected this Runestone, so there is nothing to worry about. If for some reason you did miss it, it is easier just to walk back to the switch that lowers the wall with a golem and pulling that switch to raise the Runestone, rather than starting over contrary to what the scroll says. In any case, close the scroll and exit the level.