Doomtrain GF (Guardian Force)
Once you receive the Solomon Ring (at this part of the game) you will be able to create Doomtrain, a new Guardian Force. Prior to reaching this point in the game though it is a good idea to make sure you have all of the items you need.
In order to create Doomtrain you will need the following:
[Malboro Tentacle] (x6)
[Steel Pipe] (x6)
So where can we find each of these items...
The Solomon Ring is obtained by heading to Tear's Point at this part of the game.
Malboro Tentacles can be won from or Mugged from Malboros, or you can refine the Malboro Card into a Malboro Tentacle. Malboros can be found on the Island Closest to Hell, the Island Closest to Heaven or in the Grandidi Forest, which is just outside the Chocobo Sanctuary. The Island Closest to Hell/Heaven are not reachable until you have Ragnarok, so you choices may be limited to the Grandidi Forest.
Those of you who have already completed the Chocobo Forest side quest will know that the only way to get there is to take a Chocobo from the Chocobo Forest. Just be very careful as Malboros are incredibly powerful – saving before you fight them is a good idea.
Make your way back to the Galbadia Garden area and find the nearby forest. You can Mug Steel Pipes from Wendigos.
Once you have obtained each of these materials just select the Solomon Ring in your inventory to summon Doomtrain. Make sure to have Doomtrain learn “Forbid Med-RF” first as this ability will come in quite handy later on.