That is pretty impressive! Hopefully it takes a while before I start doing in-game things in a dangerously inefficient manner where you are too polite to criticize me for it but it starts to drive you nuts.
Floor 3… is rather boring, so let’s just quickly introduce the new elements that pop up.
Annoying switch puzzles

I… may have accidentally overwritten some of the screenshots I took from this floor.
This room was basically the peak ridiculousness of this conceot. Each of those nine switches affects the eight doors in a “switch 3 toggles door 3, opens door 8, closes door 7” kind of way where you have to get all of them open at the same time. Most are less obnoxious than that, I’m sure you can get the basic idea. Worth noting is that you can click on a switch and it’ll highlight which doors it affects
Evil Eyes

…I couldn’t remember the whole room, so just the important part here. The evil eye is a giant eyeball that sits on a given tile staring in one of eight directions. The thing that makes it unique is that unlike the other enemies it only moves when you cross its line of sight (fortunately you can click on them so that said line of sight is shown). Once it sees you it heads directly for you in pretty much the same manner as your typical roach. Later on we will see puzzles where triggering them can cause serious repercussions, on this floor it doesn’t really matter all that much.
Invisibility potions

Now that I’m warmed up a bit I think I’ve got a pretty good handle on this drawing thing.
That purple bottle is an invisibility potion. Step onto its tile and…

…you become possessed by an 11-by-11 grey box! A side effect of this possession is that no enemy that is outside the bounds of said grey box can see the player. They will stand in place until you get close enough to them so that the grey box envelops them, at which point they will again attack. This makes it easier to lure one or a few enemies away from a group at a time and kill them, which is why it has often been said that Demon’s Souls is the DROD of third person action rpgs; the thief ring is functionally identical.

I put this up as it is an example of a pretty cool thing the game does from time to time. Beethro will on occasion make remarks before, during or after a puzzle that more or less function as signposts for optional but advanced challenges. Pictured here he is letting us know that one could try to tackle the room without using that potion. In the room I first drew above he will comment “I could have opened all these doors by now if I was a little more clever” if you don’t hit the switches in the optimal order. It is a really nice touch and just about the best in-universe way to handle something like this.
Force arrow madness

That room looks impossible, doesn’t it? I mean it isn’t, if it was there’s be no screenshots past this point. The trick is that there is something about these arrows that I did not mention before and that is that you can step on and off them perpendicular to the direction they are pointing. I had a great screenshot that showed this off rather well, but… ah hell, wait a sec.

While Beethro can’t go directly down over these arrow tiles he can get besides them and walk across them from right to left or vice-versa. I drew a line showing the path through the above puzzle to give a better indication as to how it works in practice.

Mimics
Mimics show up a couple times in floor 3 but are the near-exclusive focus of floor 4, so let’s skip ahead.

Those aquamarine bottles all contain the formula to create exact clones of yourself, aquamarine being the universal recognized color for clones. You take six swigs of cloning juice, partake in some puzzling and voila~

You now have a room free of pesky other living creatures and overrun by clones, clones as you know having been declared as officially not-living by Vatican II.
Mimics are a bit trickier than the other things we’ve come across on these last two floors, so let’s take a look at a typical mimic puzzle.

Mimic puzzles are often of the maze variety, this one has three mazes for the three different mimics potions available. Also noted are those tiles that fall after you or a clone steps across them as this is one of the first times they are a factor. I don’t want to tell King Dugan what’s what but large portions of this dungeon are falling apart in addition to being infested. I can take care of the latter but he should really get some contractors down here before the whole thing collapses.
Oh, right, the mimics. You sprint across that deathtrap of a bridge into section A and drink the first potion.

This potion drains all of the color out of the world and grants you the ability to hurl lightning. A side effect of this is that wherever your lightning strike lands an exact double of you is created. These clones have no brains (a running theme in this game is that everything other than you is stupid, to make up for all the times that the game makes you feel stupid) which means that they will mirror your moves exactly. You move up a square, they move up a square. You rotate your sword, they rotate their sword in the same direction. From here it is just a few turns until the one roach in mimic section A is sliced and diced (roaches observe Vatican II and will pay no attention to the mimics, remaining solely focused onto the sole living threat which is you).
The problem is that shoddy workmanship has trapped you in your little section A, the only way out being through a locked door that can only be opened by the switch that fortunately enough is located in mimic A’s section. The problem is that it is all the way across said section which is most of a 14-by-14 square, much larger than the almost 5-by-4 square you inhabit.
Fortunately there is a way around this handicap as this would be a poor place to end this game. You see…
…

…

Stupid piece of crap, “oh this is a new sessions so I’d better start labeling back at “screen01” and delete any other images that may have the same name”, no way that causes any headaches.
Oh, you’re back.
So that totally-not-hastily-thrown-together diagram shows off the other key mimic behavior. Original you is in room A, clone you is in room B with his back against a block. Original you moves backwards a few tiles but clone you stays in place because there is no where for him to move in said direction. Look back at the section the mimic is in and you’ll notice an awful lot of stuff for him to get stuck against, including a number of tiles just waiting to fall away into nothingness (mimics are at least smart enough to not walk into a pit, for them they function identically to a wall) (kinda odd that as I go down further floors I never find shattered tiles that fell from the previous floor) (you know, maybe the staircases between floors are taking me up and not down, I never really considered that).
After a bit of this and…

You are free! Free to go over and get yourself trapped in the exact same way two more times! It is either that or let two roaches live and that is one thing I cannot abide.
Bonus advanced technique: fancy edition
We’re gonna have to learn this at some point, might as well do it here.

Beethro has got himself into a bit of trouble here. As soon as he takes a step forward roaches from two opposite directions will be right on him. What to do in such a grim situation? Some of you are saying “Isn’t that a mimic bottle right there?” It is, but it is a red herring; the mimic is needed to hit that switch so that you can get that final roach in the upper right.
Now I know I sorta messed up this entry a bit what with all the missing screenshots and MSPaint stand-ins so I wanted to make it up to you. I went out and got you one of them fancy moving pictures to show you exactly what has to be done when facing such a situation. Oh don’t thank me, you all deserve it and god knows this is simpler than having me try to explain it in writing.

If you want to practice it yourself you can load up mauve’s DRODlike and try basics II (also inspired by Vatican II). Those roaches/zombies won’t know what hit them!
Double bonus: play along at home!

Here’s a puzzle I didn’t like and that took me way too long! The set-up is obvious: you hit that central switch and all those roaches are let free and head right for you from every direction. What do you do?
[spoiler]

If you are me you do the wrong thing for fifteen to twenty minutes before noticing the circled details. I diagonally stepped onto the upper of those force arrows, I didn’t notice I could have stepped diagonally down behind the arrows until after all the roaches were all dead.[/spoiler]
I think that’s an iffy lynchpin to hang a puzzle on, feel free to disagree.
Next time: hopefully no more technical issues!