These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Anvilicious: Delta's ending. The player character just will not shut up about how much better mortals are then Gods, to the point of undercutting Librom and Magusars importance.
Crowning Music of Awesome: The game features an orchestral soundtrack recorded at Skywalker Studios, and composed by Yasunori Mitsuda (of Chrono Trigger fame) and Wataru Hokoyama. The music we've heard so far seems very promising. See the main menu song and its remix for Delta.
Fridge Horror: If you save Magusar in the final battle the protagonist begin a cycle of defeating and saving Magusar over an over, while line between the protagonist and Librom becomes blurred and they become one. They fight with Magusar for years until the protagonists body breaks down and can no longer fight. Like the original Librom, they sacrifice their body to become a book that will pass on both their story and Librom's tale to the next prisoner that can take on Magusar. While scary enough on it's own, the cutscene shows SEVERAL books there, making one wonder just how many people have done this...
Game Breaker: A milder example, but some of the sufficiently powerful Stonefist spells, particularly the breakable ones from Musicians of Bremen or Red Riding Hood in Delta. While they do have a short windup, you can use them to completely pummel Archfiends who are downed, stunned or simply not paying attention to you and pile up truly mindblowing amounts of damage. For reference, the gold edition of Red Riding Hood's attack, which clocks in at over 400 damage per use, and hits multiple times in the right position. Add some damage sigils and a Dark Arm, and you're good to go.
Player Punch: A divine arm playthrough in itself. Your organization hates you because you're saving monsters instead of eliminating them, as they want, then They send bounty hunters to kill you, and you cannot save them, you need to sacrifice them to keep going. Then you're going to endure joining parties where most players have dark arm, and they'll want to sacrifice the very monsters you intend to save.
Tear Jerker: The Minotaur's backstory. All she ever wanted was a family...
The death of Similla in Delta.
Woolseyism: The Arthurian mythos references have been veiled in the US and EU releases due to some areas of Europe still treating the mythos as Serious Business, hence Nimue's name change to Sortiara and Merlin's to Magusar.