Assembly would be a good start. But to really make use of that you need to learn the internal intricacies of processor architectures and operating systems. If you want to be employable, there's just a gigantic amount of seemingly boring details to learn before you can even start to build something interesting. With high level languages you can jump into the job market almost immediately, so the cost of entry vs. potential reward is better for most people. If you don't have fun when spending years of your life banging your head while digging down incredibly complex rabbit holes, it's probably not worth it.
There's nothing too terribly special about low level wizardry, other than you really _do_ need to understand how the hardware works, and how your language works. Oddball skills you really need to know (and can easily pick up if you have a mind to) include: a) Reading processor/part data books. These are your API docs. Most of your answers are in there if you care to look. b) Reading schematics. You don't need to be able to write/design hardware, but you need to be able to figure out what each CPU pin is wired to and how you're expected to access peripherals. Again, not hard to figure out if you put your mind to it. Very handy to know: How to use a multimeter/oscilloscope/JTAG programmer/logic analyzer. There are your debuggers. You don't need them often, but when you need them, you NEED them.
This sounds like a typical embedded software engineer and I frequently see people around here complaining about the low salaries for these roles.
What am I missing?
Multiclassing is hard, but some get by as a making a divine pact and taking Eldritch Blast and Prestidigitation as cantrips. When all you have is sledgehammer, even smaller hammers are nails.
Server rez on a low level wiz build? That's way high level thoughts and prayers to the Top 500 (also a cleric build) or lim. "request" to the Blackrock genie over in Budapest. Besides, 7th? Pff, call "company of choice" to fight for you, save or die server vileness!, and of course "peon:cleanse everything? peon:what do mean everything? cleric:EVERYTHING."
Frankly you probably want a PRC, and at those admin levels much, much save or die. Probably got so many server pokes per minute you're gonna be furiously holy wording your file system all day long. Team members? Rez? Please. You solo that.
Low level wiz? "Welcome to name brand, and lack of female desirability, here's your special hat..." "Why aren't the lights on?" [1] "Help, I lit my own hands on fire!" [2] "Ah, every threat one hits me!" [3] "Man they target me bad at conferences, how'd I draw DARPA as agro..." [4] "Holy s*t there's a lot of documentation to write!" [5]
High level wiz? "Computation hates all magical ideas and their very implication!" "Curse your sudden but inevitable betrayal of my trust, our own company is secretly controlled by Orcus and seeks the death and slavery of all life on Earth" [6] "Join me in the bag within bag abyss together and we shall quest to Jubilex for glory and honor across the eternal battlefields of tomorrow!" [7] ITGETSOEPIC::THEYWONTLETULEAVE::ALREADYATWARP::AUTOLADDEREJECTED::HOWDIDRAWULTRONASAGRO::MIDASTOUCHISHORRIFYING::AHHHHHHH [8]
Unless you’re the low level wizard you’re just going to make an industry standard salary, maybe a bump but nothing special.