The easiest way to get these is from the Bomb King, and you’ll need 10 Doors for each Overdrive>AP auto-ability you plan to add to a weapon.

Where To Get Doors to Tomorrow

Luckily, Doors to Tomorrow aren’t too rare. The easiest way to get them is to farm the Bomb King in the monster arena, and you’ll get one Door per victory as a common drop. Bomb King is unlocked at the Monster Arena after capturing five of every bomb-type enemy in Spira. You can also bribe both Mech Scouters and Mech Leaders for one or two Doors, respectively. Bribing a Mech Leader requires at least 92,500 gil (for x2 Doors), while the Mech Scouters require a bribe of at least 68,750 gil (for x1 Doors). Mech Leaders can be found in the cave sections of Mount Gagazet, and Mech Scouters are all over the Calm Lands. If you’re feeling brave, you can also steal up to twenty Doors from Ultima Weapon before defeating it in the Omega Ruins. But farming the Bomb King is the quickest and most reliable way.

Door to Tomorrow Uses

Overdrive>AP is the only ability Doors to Tomorrow can customize. While it may seem useless, it’s actually key to executing the famed Don Tonberry AP trick, which can get you from sphere level 1 to 99 in a single battle. Yes, outside its use for this trick, Overdrive>AP doesn’t serve much purpose. But when utilized correctly, that can be one of the best abilities in the game. And Rikku can also use Door to Tomorrows a few powerful mixes: Final Elixir (Healing Water) – Fully restores the party and revives KO’d characters. Final Phoenix (Mega Phoenix) – Revives a party member with full HP. Trio of 9999 (Blessed Gem) – The party will deal 9999 damage with each attack for the duration of the battle. Super Mighty G (Chocobo Feather) – Applies Shell, Protect, Haste and Regen to the party.

Are Doors to Tomorrow Worth It?

Yes, but only if you’re looking to completely fill out your sphere grid. Doors to Tomorrow and their Overdrive>AP ability are vital elements to the most powerful AP trick in the game. Otherwise, if you’ve already maxed the grid, then Doors to Tomorrow could still be worth it for the Trio of 9999 mix alone – which can make battles trivially easy, including many final bosses.