YMMV / Ys: Ancient Ys Vanished ~ Omen

• Complete Monster: See here.
• Demonic Spiders: Enemies in the lower mines for Ys I: Ancient Ys Vanished - Omen, especially in the Ys Eternal port, mainly due to their movement speed and attack power, coupled with the mines' limited visibility. Elite Mooks in the upper levels of the "Darm Tower" can also quickly mow down players, even if they have the best armor, shield and weapon in the game equipped.
• Ensemble Dark Horse: Dogi in Ys I; due to his popularity, he has became a Breakout Character who went from a random side character who helped break out Adol in Ys I to his only permanent traveling companion.
• That One Boss: Vagullion is the point where a lot of players tend to hit a wall. Splitting apart into a horde of bats, he chases you around the room and occasionally reforms for the span of a second. Every single individual bat damages on collision and can be spread apart pretty wide, making Scratch Damage almost inevitable, and even circling the room doesn't work consistently. Get yourself caught in the swarm and you'll lose health fast.
• That One Level: The "Tower of Darm" in Ys I, a 24-floor tall structure taking up a good half of the game, has a confusing maze-like environment that's easy to get lost in, features a gratuitous instance of back-tracking at the very end (such as a mandatory traversal back down the tower to collect the "Blue Armlet" accessory), contains several Guide Dang It! moments, and is full of Demonic Spiders. This is before mentioning Adol loses his best equipment six floors in due to in-game events, and retrieving them is seemingly optional.. until it turns out they're necessary to even hurt the Final Boss, much less not die in five seconds.
• Viewer Pronunciation Confusion: The title screen of the English Sega Master System version attempts to avert this by adding an IPA guide◊ next to the title. However, if you didn't notice the guide was there (it's easy to miss), or didn't realize that it was a guide, or didn't know how IPA pronunciation works, then you'd still be out of luck. Exacerbating the problem, the rear description◊ spells the game's title as "Y's" with an apostrophe, leading to it being widely mispronounced as "wise".
• Woolseyism:
  • In the first ten minutes of Ys I of Chronicles Plus, Slaff warns Adol of Nurse Ayla's formidable temper by singing the chorus of "Maneater" by Hall & Oates to him.
  • Another attempted example Hudson Soft did was change the name "loo" to "quay" because the former is used in British English slang to mean "toilet". However, it didn't stick, and subsequent localizations changed the name to "roo".
  • Hudson Soft renamed the Fukt family the Fact family, which is the name most English localizations used. However, the original name might have been turned into a hint as to the family's status because Cain Fact did turn all of its members into demons or human demon hybrids.