In order to acquire Lulu’s Celestial Weapon, you need to have full control of the airship, which will happen towards the end of the main story. Once you do, you will need to go to the navigational controls and use the Search option. Look around (X: 15, Y:55) or so to find Baaj Temple, which is where you were towards the beginning of the game. Travel to that location and jump in the water, where you will want to swim towards the entrance to the temple.
If going in the right direction, then you will come across a familiar face, Geosgaeno, a boss you faced early in the game. This time, however, you will need to defeat it, although the creature shouldn’t be too much of a challenge for you. Just make sure you don’t defeat it should a character be in its belly. Once you defeat Geosgaeno, swim to the opposite side of the entrance to the actual temple. Look for the little area where the camera angle changes, then continually press the interact button on the right side until you open the chest with the Onion Knight inside. The chest is out of sight, so you won’t know until you actually get the Celestial Mirror prompt.
Fully powered up, the abilities on the Onion Knight are:
- Break Damage Limit
- Triple Overdrive
- Magic Booster
- One MP Cost
The Venus Crest can be found on the Farplane in Guadosalam, as soon as you’re finished there during the main story. Once you gain access to the Thunder Plains, head back to the actual Farplane and there will be a chest on the left side, which contains the Venus Crest.
The Venus Sigil can be one of the more frustrating pieces of a Celestial Weapon to get, as it involves you doing the Lightning Dodging minigame on the Thunder Plains. To get the Sigil, you will need to dodge 200 consecutive lightning bolts, which can be a huge problem, as it’s not the easiest thing to do. Before even thinking about it, you will want No Encounters on a piece of equipment, which can either be dropped by the Ghost or Wraith enemies, as well as customized with 30 Purifying Salts. Note that Geosgaeno can also drop a piece of equipment with No Encounters on it.
Once you have No Encounters, head to the southern section of the Thunder Plains and look for a lightning rod tower that has a crater just north of it. It will be on the western side of the main road that cuts through the area. Approach the crater to trigger a lightning strike, then run back to the tower to reset it; keep doing this over and over. Note that while the game tracks your lightning dodge count, there is no actual visual count shown on your screen, so you will need to keep track of it on your own. To be on the safe side, do an extra 10 or 15 extra lightning bolts, so when you head to the chest outside of the travel agency, you guarantee you get the Venus Sigil.