DM: Alright, I take it Twilight fires some Magic Missiles at the crystal walls?
Twilight Sparkle: I guess. It's at-will and Force damage. Should I roll Arcana to add some extra oomph to it?
DM: Well, hold on, I'm going to give you some information first.
SFX: (PING!)
DM: A quick test-fire reveals that the crystals can reflect low levels of magic.
Twilight Sparkle: Oh. That's not good.
DM: Your Magic Missile bounces around the cave, gaining more speed and power, until... <roll> ...it impacts the hard rock just a couple feet away from you, leaving behind a small smoldering crater.
Twilight Sparkle: Woah! ...Wait, you weren't rolling to see if I took random damage, were you?
DM: No no, just rolling for how close it got and whether you needed to dodge, which would have been trivial.
Twilight Sparkle: Thanks. Still, that's... significant data, actually. Is there some way I could harness this reflection-magnification property to strengthen my spells?
DM: You want to focus on escaping without a cave-in first?
Twilight Sparkle: No, that's what I mean! Tap on the walls to find a shallow point, and calculate the correct angles to reflect a Magic Missile that would break through it.
DM: Oh. That's... smarter than what I had in mind.
This is kind of the fantasy I'm hoping for when I roll up an INT character. Using the power of Smarts and Science to overcome obstacles where my unreliable STR would fail me.
In reality, it just kind of boils down to... "I cast the spell that according to rules-as-written will shut down this entire encounter. Either they save or they don't."
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That's the advantage of being an illusionist. With the power to make your opponents see whatever you want, you can compel them to do anything you can make the GM think is reaosnable.
The downside, of course, is that most of your powers depend on convincing the GM that the result you want is reasonable, so, depending on the GM, you range from so overpowered it isn't even fun down to completely useless.
Only thing I can think of to this topic: For one of my favorite systems (Dungeonslayers) I once created a special talent that allows you to apply your INT to feats of strength.
I called it "Lift from the Legs!"
D&D 5e's Battle Smith Artificer has an ability like that.
Battle Ready-
When you reach 3rd level, your combat training and your experiments with magic have paid off in two ways:
*You gain proficiency with martial weapons.
*When you attack with a magic weapon, you can use your Intelligence modifier, instead of Strength or Dexterity modifier, for the attack and damage rolls.
I mean, my Pathfinder 1 cleric 'Azure Studies', is basically powered by her smarts. As a follower of Twilight Princess Luminace, she's got knowledge domain, and thanks to a couple ponyfinder feats for unicorns (Practicised/Advanced Horn Magic for combat horn grips, and 'Outwitting the Divine' for cleric stuff to run on INT instead of WIS), I pour all the points in INT and destroy things with the power of SMRT! (like, when the campaign basically died off that I was playing her in, she was a natural 20 INT at lv6)
And this is why trust passwords and security measures are important. Twilight could have stopped this whole mess before it started if she had just asked Cadance something she should have known — the Sunshine Sunshine mess would have been a great thing, had Twilight not shown her hand by prompting with the rhyme instead of getting Cadance to say it.
In reality, it just kind of boils down to... "I cast the spell that according to rules-as-written will shut down this entire encounter. Either they save or they don't."