Mysterious Adventure

*For the sequel dungeon of the same name, see Mysterious Adventure (Sequel)*

The Mysterious Adventure dungeon is the main endgame dungeon that doesn't unlock until you've cleared the first six dungeons. It has random floors and random monsters, so it will be very different every time you run it. Most dungeons have each floor have a fixed set of monsters available and a fixed setting. The Mysterious Adventure dungeon randomizes them every time, so the mobs you see on level 50 in one run might be totally different from the ones you see on level 50 in another.

Mysterious Adventure floors come in sets of five, with a new set chosen randomly at every multiple of 5. Five consecutive floors thus have the same basic design parameters and the same monsters available, and then the next set will have a completely independent choice. The Japanese wiki says that the dungeon has 999 floors, but I haven't verified this. You can bring any friends or gear into the dungeon, but as with most other dungeons, many items start out unidentified.

As you go to higher floors, the monsters become higher level. One way to think of it is that there is some base level for a dungeon floor, and each type of monster has some offset that reduces the actual level of the monsters. For example, if the base monster level of a floor is 20 and a slime has an offset of 0, then (blue) slimes on the floor will be level 20. If a lamia has an offset of 5, then lamias on the floor will be level 15 (= 20 - 5). If a blue dragon has an offset of 25, then blue dragons would have level -5, so they cannot appear on the floor at all because all monsters must be at least level 1. I'm making up numbers here, but this model seems to fit how the dungeon works pretty well.

Most but not all of the recruitable monsters are available in the Mysterious Adventure dungeon. In particular, the two strongest monsters in every single group can be befriended there, though some won't be available until far into the dungeon. I'm not sure what the minimum floor required for all monsters to be possible is, but my best guess is somewhere around floor 400. Note that once you reach a high enough floor that a given monster could appear, it won't necessarily appear immediately, as each set of five floors has only a handful of fixed monster types. So once you reach the minimum floor where a monster could appear, you might not actually see that monster until 100 floors later.

Swords and Shields do not drop in the Mysterious Adventure dungeon, other than as drops from Alpha Monsters. Alpha monsters can become incredibly powerful as you get to deeper floors, however, so you'll probably want to avoid them once you get very far in. The dungeon does have a hard level cap of 200 for monsters, but a level 200 alpha monster is nearly unbeatable unless you can keep her mostly disabled by various status conditions.

Once you reach floor 201 of the Mysterious Adventure dungeon, subsequent runs will give you the chance to jump there directly from floor 4. The same is true of floors 401 and 601. I have not reached floor 801 to know if it is also available as a starting point. Getting started at a low level against the foes you'll face on floor 201 is tricky, but you can level up quickly, and if you're trying to push friends to high levels, this is by far the fastest way, as you can jump in directly against mobs that grant 1000 experience each or so. If you want to start on floor 401, you'd better have some very strong friends or else you're going to be very dead, very fast.