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.
At the end of the Scholia Arcana questline, the Dark Empyrean will still be at the same level she was at when you first encountered her in the questline's first quest, whereas you've more than likely leveled up several times since then.
Designated Hero / Designated Villain: The principal players of the House of Ballads tale are in-universe examples. The Maid is sick and tired of her role as a villainous loser, while the "heroes" this time around ultimately don't live up to their roles. King Wencen reveals himself to be a Dirty Coward when he realizes the Maid could actually win this time and tells you "Here. You're King Wencen now." before running for the hills.
The mage's Meteor spell can instant kill everything in a large area that isn't highly resistant to fire. That pretty much means everything but trolls and Niskaru Lords become laughably easy.
The game has a potential equipment effect that reduces casting cost, but the internal calculation is wonky. Not only does the effect reduce the cost by a flat percentage rate, not a proportion -at one hundred percent reduction, spells are free- but it stacks multiplicatively, so you really only need about 85%, or so. This isn't hard to get,note You can get 40% reduction from two rings you'll earn as part of the Scholia Arcana questline, another 20% from the higher-level Sorcery destiny perks, another 20% with but ten points invested in Sorcery, and a final necessary 10% from a purple helmet you can find in the first area after the tutorial. and since high-level magic is balanced by casting cost, not recharge time, (all of which are relatively negligible.) you can use all of your gear to upgrade your health and armor, instead. It's almost impossible to lose at this point.
As with most newer Western RPGs, liberal use of crafting, namely blacksmithing, takes any semblance of difficulty and pounds it into oblivion. Maxing out Black Smiting can be done hilariously early, especially if one chooses a race that gets a bonus to it. Load up on health and mana regenerating components/gems, grab the crappiest weapon and armor of the highest type you have access too, save scum a little to make sure you get the base crafting item out of them, mix it all together and you are wearing clothes and wielding swords that are twice as potent as even the strongest items you could possibly have access too, at less than a tenth of the cost of actually buying a piece of gear that would laughably be called comparable, and allowing you to sell the immensely valuable gear you'd normally want to wear. Enjoy virtually unlimited gold, health and mana.
Also "Reckoning mode" is essentially an "I win" button. It slows time and boosts your damage output to ludicrous levels, making any fight in the game laughably easy.
There's the scattershot ability, which when combined with other longbow abilities, all bleeding related abilities and the right armor can deal thousands of damage total, is more or less guaranteed to cause bleeding and potentially poisons the target too. ( Also, you can make poison propagate to other enemies and bleeding can randomly deal a lot of bonus damage. With this setup even the normally weak shadow weave ability ( which is supposed to enhance your attacks rather than actually being one ) can oneshot a prismere troll.
You can kill a Jottun with basic stealth. Or an entire army of them. Or kobolds, or anything else for that matter if it isn't a troll or niskaru. In fact, with the smokebomb ability you can backstab most humanoid bosses, killing them in a single hit.
Most enemies have a weapon type that just erases them from existence. Chakrams are useful against giant-type enemies, and Squishy Wizards go down with a few greatsword hits.
Goddamned Bats: Wolves especially early in the game. They come in packs and tend to coordinate their attacks to flank you, they also stay out of your melee weapons reach and can cause the Bleeding effect which slowly drains your health and decreases your Physical Defense.
Boggarts are at most a nuisance even at the very beginning, however they can distract or stun you enough for a Thresh to land its dangerous attacks on you.
It's Easy, so It Sucks: A common complaint about the game; since the game is so combat-focused, most character builds are ridiculously overpowered, and whatever little challenge the game provides can be mitigated with potion-and-Reckoning abuse, most players can overlevel and breeze through the game before they know they've done so. It doesn't help that you have to actively try in order to avoid the Gamebreakers.
That One Boss: Mage type bosses like the Maid of Windemere, the Dark Empyrean, and Templar Octienne can be fairly challenging given their variety of powerful elemental ranged attacks, teleportation abilities, and constant summoning of mooks. Especially jarring given the relative ease of the game. Reckoning does make them considerably easier, but if you don't have a full Fate bar or a Fate potion ready, death is a real possibility.
Also extends to Boss in Mook Clothing like Bog Threshes or Crudoks. Groups of Sprite Champions can also be a real handful if you're not prepared to instantly take them out. Sprites can use weaker variants of the Sprite Champion, Champions can use other Champion's attacks as well. For mages this is particularly hard as Sprites get elemental resistance from their Champions, and most of a mages' weapons and offensive abilities deal elemental damage. For the same reason Trolls tend to be tough fights for mages, they have very high elemental resistances.
That One Side Quest: "The Guiding Hands" can become this if you haven't been leveling your Stealth skill up to that point.
"The Killing Ground". You need to escort a suicidal warrior with pitiful health and defenses through hordes of Tuatha and Prismere Trolls.