Grimrock

I'm on Clash Beach. I assume the strategy here is not to face-tank the ratling bosses... so I turned to the "Elixir Collector". The only thing I can think of is to drop a potion in the teleporter, but because of the lack of a floor on the other side, the game doesn't seem to allow this. Am I missing something here? Thanks!

You can break through the walls on the left and right side, but that leads to those stationary Ratling bosses. Face-tanking is definitely not the best approach but it is possible to "snipe" them. If you have Firearms Level 3 you can hit them without them reaching you. Using Throwing Weapons, Magic bolts, or even the Bow/Arrow can take them out from a safe range. Although, killing the Ratling Bosses on the beach won't accomplish much since the goal is to get in to the center. If you do kill these Rat Bosses you may find Item rewards, but nothing required to beat the level.

To get in to the center, breaking through the bottom walls is required. Inspect the bottom section walls carefully to avoid setting off multiple "traps."

The Ietter to Catherine says to go down in to the Chamber and enter 1 on the Left button and the Total island Markers on the right Button. The Total Island Markers count is 8. Once you do that, pull the lever and a Scroll is revealed. Its contents advance the story but also give you a clue as to what to do with the figurines.

The first figurine is the skeleton, found on the beach dock. When you go to the Library and place this figurine on the Altar, the hidden wall text shows the key:
'East-West'
'North-South'
'North-East-South'

Go to the building next to the Library (where you found the Compass) and stand in the center. Using your compass, place an item on the East plate and the West Plate. Now walk forward and pull the lever at the end of the room. A portal will appear; this will take you to a room that contains a monster. Write down which Monster this is.

Take a portal back up and repeat the process for the North/South plates, as well as the North/East/South plates. This will give you 3 monsters total. Now walk outside and place an item on the plate that corresponds with those monsters. A secret is revealed.

For the rock puzzle, simply place the Ogre figurine on the altar in the library. The hidden wall text will reveal the combination: 7-4-2. Go back to the room where you found the Ogre Figurine and, from left to right, place rocks inside each of the 3 Alcoves. Starting from the left: the first Alcove gets 7 rocks, the second gets 4, and the third gets 2. Now pull the lever. A secret is revealed.

Use the remaining figurines on the altar to get the keys for those combinations as well. Note that once you have completely unlocked Myst Island, I would recommend that you first travel to through the trap door located on the dock. As the other locations are pretty difficult if you have a beginner party.