I wouldn't call luck itself a skill, but the abilities to capitalise on luck and to solve issues that might arise due to lack of luck are certainly skills.
Denken (German for "thought") might be an old shrewd man, but he's still not heartless. It's one thing to kill your political enemies to further your goals, but killing a kid (they're both kids from his PoV) when there are other solutions is another matter.
Fern's poker face comes handy at those times. Raised by a Frieren that shows almost no emotion. As well as her "stick to the fundamentals" approach, like hinted in ep19 fighting her is more like fighting an old mage than a kid.
I wouldn't call luck itself a skill, but the abilities to capitalise on luck and to solve issues that might arise due to lack of luck are certainly skills.
That is also my take away from watching streamers play roguelike games. The not so good players want to be dealt good hands, but the good players can do well (or at least not lose their run) even when not favored by the random number generator.
This is along the lines of a quote by Louis Pasteur that I use all the time with student and junior scientists at work, "chance only favours the mind which is prepared" basically meaning that you can only get lucky if you are open to and prepared to take advantage of it. The history of the quote is also a neat confluence of physics (my field of study) and microbiology (similar to what I do professionally), so it has stuck with me through the years.
I am so glad to see Denken doing his thing. He is one of my favorite characters from this series outside of the past/present main party. Also, Fern continues to surprise demon and human alike with her ability to mask mana.
Yup, that's exactly what I'm talking about; finding the yeast and lactobacilli in the beet juice was luck, but actually associating them with alcoholic vs. lactic fermentation requires that sort of knowledge that only comes with diligent experience. (Another case that comes to my mind is Fleming and the penicillin. )
About Denken, I feel like it's one of the things that this series does the best - even the side characters show some depth.
Oh, I still find it funny that Frieren can detect that she was detected by Denken. It is like a submarine operator saying "we have been detected by passive sonar!" which makes no sense but I guess magic doesn't work that way.
Alright, so this week we kind of get a vague answer to the thread last week asking how Fern's party caught a Stille. I honestly did not remember them bringing it up at all in the source, but I just went and checked and here is the page in the manga (chapter 42, page 2 if the link doesn't work for you).
Also this episode, we learn about the mysterious, dark figure that has been in both versions of the OP so far, Serie. She has promised to grant anybody that earns the title of First Class Mage any one spell of their choosing. Any guesses as to what Frieren or Fern would ask for?
Finally, I just wanted to mention that something I like about this arc is how talkative all the mages are. They are all too happy to show off their magic, explain how it works, and monologue about why they want to be a First Class Mage. In a lot of other series, this tends to bother me because when people get into a fight, they don't usually do that, they just run at you and beat you up.
However, I think it fits thematically in this series with the way mages have been portrayed. I think this kind of thing, showing off and flaunting your magic, is the kind of thing that Flamme, Frieren, and finally Fern just don't do. I think that is part of what makes their fighting style so disrespectful to other mages, like was discussed back in episode 10. By hiding their power and not engaging with other mages using their all, it is kind of like breaking the unspoken rules of honorable mage fighting, like a chivalric or bushido code that mages are expected to abide by.
Anyway, this is something I hadn't given too much thought about back when reading the manga, but with all the renewed discussions about this series as people are watching the anime, it is causing me to think on these things that I hadn't paid too much thought to before.