The completed Triforce awakens Princess Zelda and ends the campaign.
Optional
The final Link Doll is optional but valuable for the boss run. Great Palace red potions are worth detouring for when resources are low.
Missable
Link Doll #6 is permanently lost after completing the Great Palace. Take the left branch at the late three-way elevator before the final bosses.
Numbered 100% route
Cross into abandoned Old Kasuto. The Cross makes the invisible Moas visible; enter the first house and learn Thunder from the Wise Man.
Enter the Valley of Death from the nearby graveyard trail. Take the early lava-fork dead end for a point bag if safe, then continue north through the forced battles and caves.
Use Jump over wide pits, avoid unnecessary Lizalfos fights when low on lives, and enter the Great Palace. Continue after a game over to restart at this palace entrance instead of North Palace.
Pass the released barrier, descend the first elevator, and take the left route. Jump the false floor after the pillar and continue generally east and down through the palace.
Use hidden wall passages beside elevators for red potions, and use Upward or Downward Thrust against Fokkas, block floors, and the Giant Bot.
At the late three-way elevator, take the left branch to collect Link Doll #6. Return, descend, and fall through the invisible floor beneath the fifth and sixth blocks.
Cross the melting bridge and deliberately fall through the gap in its center to land near the final route. Restock from the left-side blocks only if the Fokka risk is acceptable.
Enter Thunderbird's room with at least half magic. Cast Thunder once to expose its face, then use Shield and Jump while striking the face directly.
After Thunderbird falls, take the Key and face Dark Link. Fight normally by controlling space, or use the reliable corner defense if you only need the clear.
Claim the Triforce of Courage and return automatically to North Palace to awaken Zelda.
Boss strategy
Thunderbird is invulnerable until Thunder changes its color and exposes its face. Thrust techniques do not damage the face; use direct sword slashes.
Stay in front of Thunderbird when possible because its falling fire travels behind it, and use Life only if enough magic remains after Thunder and Shield.
Against Dark Link, a disciplined corner stance with repeated low slashes minimizes the angles he can use.