What Makes Shadowdark's Spellcasting Great AND How to Use It

Shadowdark has one of my favorite magic systems. Here is how it works and why I love it.
Magic in most TTRPGs is super predictable (which is fine) but in Shadowdark they really capture the chaotic and dangerous nature of magic which I love because it makes it feel more interesting and risky. Who doesn't like a little risk in their games? (I know. A lot of people don't, but I like it and that all that matters...right?)
Have fun adventuring!