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WW - Sunken River Area
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You enter facing W and then turn immediately S into the first Cavern.
As you enter a Kabasaur will appear. This tall, pale, fat version of the Creature from the Black Lagoon is slow but Strong! He will take you down in only a few hits if you give a chance. Stay to his side or behind him and use slashing attacks. He will drop the second Floodgate Key. Watch for his buddy to appear before picking the key up. Finish, and then move into the wide corridor that leads into the Deep Pool room.
This large room has a deep pool of acid in the middle of it with a walkway over the middle of it. You enter from the E. The Kabasaurs appear up around the edge, mostly in the SW area and the Water Knights appear down in the bottom of the pool.
Move counter-clockwise around the pool, towards the N side and then down the W wall until you come to the corridor in the W wall that will lead to the Save point. Save.
Now re-enter the DP Room and engage the Kabasaur(s). You will hear and notice that there are Water Knights in the Acid Pool. Ignore them for now. You will lose HP and equipment (rapidly) if you engage them while they are still in the acid. It is now time to drain the swamp.
Move into the SW corner and into the doorway there. See the Face looking at you on the wall? Well, down in the acid here and to the W a bit is a chamber with a pedestal that takes the first Floodgate Key. Decide if you want to wear armor or not. There are no creatures to fight. Jump in and use the Floodgate Key. Now quickly move back to the E and find the corridor through the acid heading E. Follow is and just after you go up some steps and out of the acid, you will fins a Cune. Re-equip yourself and follow the corridor around. At the T intersection, you will see a Kabasaur to the W and a room with a Soul Pod +14 in it. This is also a room you will Warp into from another Warp point on this level. The Kabasaur never Dropped anything for me. Take it out.
Return to the Face area. Another pedestal has appeared here that takes the second Floodgate Key. This will do 2 things. First it drains all the Acid from this level (Yayyyyyy) and second, makes it possible to access a weird looking treasure chest in the chamber down below the Face on the wall. Of course, you must obtain the Mermaid key first. The chest contains the Sorcerers Ring of Frost. Once you go down there, you will find the only way out is a Warp point in the NE corner of this lower area. It leads to the room mentioned before that was nest to the Kabasaur.
Now you can drop down into the Deep Pool area with the Water Knights in it. Save first, of course and take out any Kabasaurs that appear before you jump down. There is no coming back this way once you do unless you have a Sacred Feather on you.
In the W section just under the bridge above you will find the Shield. Battling the Water Knights is best done close up and you should be in constant motion. Move away from them and watch them approach. They jump up, do a corkscrew rotation towards you, like a bullet or arrow will, then land and hit you. The corkscrew attack is worse than their bite. So stay close and use the Swing-Magic-Swing type of tactic, constantly repositioning yourself. Again, no Acid magic, obviously. One of the last ones you will encounter will drop the Mermaid Key. You may have to come back through here again later on in the game to encounter this last Knight. I sure did. In all 3 games I played through.
The way out of this level is through the corridor to the N that is under the bridge that runs over the Deep Pool section. Be sure to pick up the bracelet on the way out.