Hello there, so I was passing buy and decided to join the discussion.
To begin with, addressing the difficulty name: using synonyms that require users think and actually look up in a dictionary would be good for a spell'n'check game, we'd prefer something with clear relevance to the song. After all, if you want to go for it, why not just name it Phantom World or Phantomworld. Tat seems to be way more obvious and uderstanable.
Can we talk about the 1/4 spacing usage in the Shadowland difficulty, while we are at it. I don't quite get why the intro part and patterns like 00:08:499 (3,4,5,7) - 00:12:107 (1,2,3,4,1) - these use far more intense spacing values than beats that have much more intensity and support in music during the kiai(!) section. For example, 01:05:461 (5,6,1) - 01:10:967 (3,4,5). It makes me feel like the intro should be toned down in general.
Moving om, I have to agree with something Sonnyc has brought up as an issue. 00:17:423 (5) - and 00:18:183 (7) - despite being playable, they are very similar to the 1/2 sliders slightly reduced in length. Which is what players are very likely to believe in, since there is a plenty of slowdowns, the 3/8 sliders are very likely to be misread, causing further confusion on 00:18:942 (7). It does not feel like an intended reading difficulty but rather a possible misleading pattern.
I would also have to agree with 00:19:702 (3,4,5,1) - being somewhat tricky. The fact that (1) is stacked does contribute to reading difficulty as well. And while it can be read and played by highly skilled players, being inconsistent and unmatching with the target difficulty of an Insane level, this pattern just does not feel like it should be here at all, if you ask me.
00:51:790 (6,7,1) - this, however, appeared to be just fine to me. It sure is an unpolished pattern, but there are certain patterns like 00:32:423 (2,3,4) - that slowly get players ready for 00:51:790 (6,7,1). therefore, making it readable and matching with the context of the style/difficulty.
Stacks 00:41:157 (3,1,2,3) - here caused a bit of confusion as it did not line up with the rest of 1/4 stacks followed around. Using different placement or spacing could help.
I also find 01:25:303 (6,1) - 00:24:543 (8,1) - 1/4 jumps quite inappropriate. I think you intended to justify them with the fact that sliders are made in a way that hitting them earlier still gives you a 300, but that does not feel quite convincing. To begin with, these two do not feel quite consistent with the rest of the 1/4 patterns and on top of that, they do put a lot of extra stress on a player, which probably is an overkill for an Insane. On top of that, score V2 would considerably hurt the playability of these two specific patterns, prodcuing artificial and probably unwanted difficulty spikes.