Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Master Pakku becomes tapped, target player mills X cards, where X is the number of Lesson cards in your graveyard. (They put the top X cards of their library into their graveyard.)
Master Pakku is a mono-blue Lessons-matters mill/spellslinger commander. You stuff your graveyard with Lesson cards (by milling or discarding yourself), then repeatedly tap Pakku to grind opponents' libraries down while Prowess lets him swing in as a steadily growing evasive-ish beater. Lean on cheap noncreature spells to trigger Prowess and on tap/untap engines to fire Pakku's mill multiple times per turn.
Two-mana commander that comes down early and starts pressuring the board with Prowess.
Built-in repeatable mill that scales as your graveyard fills with Lessons — no card investment needed beyond tapping.
Mono-blue gives deep access to card draw, counterspells, untap effects, and tutors to assemble loops.
Flexible: can pivot between dedicated mill and a spellslinger/Prowess tempo plan.
The mill trigger is tiny without a critical mass of Lessons in the graveyard, and Lessons are weak standalone cards.
Single-target mill (one player at a time) is slow against three opponents in a 100-card-deck format.
Heavily commander-dependent — removal or repeated tax shuts off your engine.
Mono-blue lacks graveyard recursion and broad board wipes, so a stalled engine is hard to rebuild.
Mill is a famously inconsistent win path in EDH unless you go all-in.