Spell Backpack 2
Artifact Magecraft — Whenever you cast or copy an instant or sorcery spell, put a book counter on Spell Backpack. T, Remove a book counter from Spell Backpack: Add C. 3, T, Remove three book counters from Spell Backpack: Draw a card.
Most magecraft triggers will be triggered on purpose. This one is meant to sit back, absorb triggers, and occasionally be useful.
This must have been nerfed at some point in development. I wonder how it started... Mana of any color? Not tapping to activate? Less/no mana for the draw ability? Only one or two counters for the draw ability?
Yikes. There were several ways of making this better. Dropping the cost to 1, not requiring removing a book counter for mana, or dropping the ability cost on the card draw since you need to cast three spells to get there. This is an uncommon that I'd be angry to open.