I came up with this tutorial as i was doing some reworks on some merch for The Flatliners. I needed to quickly crop a portion of the text I was changing on the fly so i ended up using a transparency mask instead of pathfinder tools. It saved me a lot of time and it also reminded me of how big of revelation it was when i learned how to use them a while back. I had always assumed that alpha channels were a luxury of working in raster editing software only. Turns out i was wrong. There are absolutely in Illustrator too and can be an invaluable tool.
This is just a brief overview of how they work, hopefully it makes sense. If you want to see more about this possibly doing some other effects or just need some clarification, hit me up in the comments. Sorry in advance for the shaky cursor and stuttering too, i think i had two huge cups of coffee at the time of filming.