Ruy Lopez Morphy
The full White-side Spanish: ten branches from 3…a6 — Closed Chigorin / Breyer / Zaitsev, Marshall, Open, Exchange, Steinitz Deferred, Arkhangelsk, Worrall and Centre Attack — each drilled twenty book moves deep.
The Ruy Lopez is the king of king-pawn openings — Morphy, Capablanca, Fischer, Kasparov and Carlsen all built their White repertoires on 3.Bb5 a6 4.Ba4. This pack drills the ten branches you actually meet: the three Closed mainlines (Chigorin, Breyer, Zaitsev), Black's two big counterstrikes (Marshall and Open), the structural Exchange ending, the venerable Steinitz Deferred, the modern Arkhangelsk, plus White's two early sidelines Worrall and Centre Attack. Twenty book moves per drill, forty exam positions covering the critical decisions — when to play d5, when to retreat the bishop, when to lift the rook on a3, when to break with f4. Finish the pack and you are not memorising moves, you are playing the Spanish.