One thing I struggle to conceptualize in the fiction is how a mundane set of thieves' tools can defeat a magic spell. Like, what is the character actually doing in this instance? Is it purely a game mechanic thing, or can it be given a reasonable explanation within the context of the game?
Good question!
I'll start with a Doylist explanation (never mind in-universe for a minute, let's see what the story is
for). Spells don't exist. A magic trap looks like whatever the worldbuilder – in this case the game designer – chooses. And the game designer had BETTER choose what makes for a better game. And I, for one, think the game is better when a Master Thief with zero magic
can, in fact, disarm the spooky magic trap, as long as they're so good at their job and so damn lucky that they can beat a "nearly impossible" skill DC.
Now to the Watsonian explanation. Okay, but it still has to sound believable to be satisfying, right? It has to make sense in universe. Well, it does! All 5.0 Arcane Lock does is magically lock the door. (Reminder that Eye of Vecna is still with the 2014 rules.) It may be magic, but it's still a lock. You can pick a lock. "While affected by this spell, the object is more difficult to break or force open; the DC to break it or pick any locks on it increases by 10." There.
But why do you need proficiency in thieves' tools for that? Shouldn't anyone be able to deface the glyph? Wouldn't having proficiency in Arcana make more sense?
For the glyph example, it may be designed in such a way that most attempts to deface it will simply trigger the trap. But if you're exceptional in using Thieves' Tools (or Arcana, sure!) and do it with perfect precision, you might be able to pull it off. Doesn't that make sense? Doesn't it leave our suspension of disbelief alive and well?
IRONICALLY, 5.5's Arcane Lock does not add a +10 to the DC, it unceremoniously makes it impervious to non-magical means. And I HATE this, I hate how a 2nd level spell can shut down mundane characters of any level. Like how in 3.5 the poor Ranger was supposedly this legendary tracker, who at Epic levels could take an Epic feat and track a creature across water and through the damn air, and STILL couldn't bypass the hurdle of the level 1 spell Pass without Trace.
The problem (and it's a problem with D&D across editions, I think) is that too many spells go straight to describing their effect, often a powerful and absolute effect, without describing how the effect is achieved. It's magic, we're done. Well I think that's bad and boring.
"You touch a closed door, window, gate, container, or hatch and magically lock it for the duration", says Arcane Lock. Okay, how? How is it locked? Does the spell conjure a locking mechanism? Does it create a barrier that prevents the door from moving? Does it repel things when they get too close to the handle? What does the spell actually DO?
3.5's Pass without Trace said
"The subject or subjects can move through any type of terrain and leave neither footprints nor scent." Okay, how? Wouldn't it be incredibly more flavourful if it said that the local flora and the ground itself briefly animate and sweep the tracks, for example?
And then both spells say that they're simply unbeatable by non-magical means. And here's the thing, if the effect is not too powerful and/or not too absolute, that's okay, I'm not gonna make a fuss. But when it is, when most spells are like that, I have a problem.
We often say in D&D that if it has stats, you can kill it. Here's another aphorism: if you know how it works, you can be creative, and deal with it in a million different unpredictable ways. If the effect is merely
stated, without explaining how, the only way to handle it is what the designers predicted. And sadly they didn't predict much.