You should find yourself out on the world map, over which the city of Esthar sprawls. Looks like an ecological disaster... Oh well, bring up the large world map and you should notice five new map markers on the continent of Esthar - Esthar/Airstation (which you're just south of), Lunatic Pandora Laboratory, Esthar Sorceress Memorial, Lunar Gate and Tear's Point. Your goal is Tear's Point, which is the southeastern-most of these markers. To get there, follow the road south, turn left at the first intersection, then continue following the blue road as it bends north. When the blue road forks, continue north, and when it forks again, follow the right-most blue road, then take a red road to the right to leave the city limits and get your feet back on earth again. From here just head east and south to find Tear's Point.
Enter the location and follow a road up, then on the next screen note a Life draw point, if you need it, but otherwise keep heading up. On the third screen, continue up to reach a series of massive, sitting statues. Approach these statues to find a Reflect draw point and an object on the ground - search it to score a Solomon Ring.
This is the final item you need to summon an obscure GF, or at least, the item this GF requires that can be found furthest into the game. Other required items include six Malboro Tentacles, six Remedy+ items and six Steel Pipes, all of which could have been gathered earlier. In case you missed your opportunity to gather some of these later, their locations will be discussed below, although you may have to wait a bit to acquire the freedom to roam and obtain some of these items:
Malboro Tentacles: You can score these by defeating Malboros, which you can find in various places on the Esthar continent: on the western coast of the Esthar continent, near the entrance to the Great Salt Lake, just outside Tear's Point in Esthar's Abadan Plains (stick to the rocky parts, not the sandy parts) to the north of Esthar City (Nortes Mountains) and a few areas you can't access yet. If you go hunting them, just make sure you're in the right place by checking the bottom of your menu screen.
You can also get this via Card Mod, as four Malboro Cards turn into one Malboro Tentacle - twenty-four cards is a bit much, but it's an option.
Remedy+: Probably the easiest item to obtain, you can get these by using Alexander's Med LV Up ability to turn ten Remedy items into a Remedy+. Sixty Remedy items will get you the six Remedy+ items you need. Remedy items can be purchased from a variety of shops, including Balamb Shop, Dollet Shop, Timber Shop, Esthar Shop, Man from Garden and Esthar Shop!!!. With all of Tonberry's abilities, this should set you back 45,000G.
Steel Pipe: Perhaps the most common item, you can get them from GIM47N and Wendigo enemies, the latter of which are probably more easy to encounter. You can find Wendigo enemies in forests near Dollet and Timber, to name a few place. You can also obtain Steel Pipes by using Card Mod on the Elastoid Card - one card, one pipe.
When you have all the items above, go into your inventory and use the Solomon Ring. The items will be consumed, and you'll earn the Doomtrain GF.
GF - Doomtrain
Doomtrain is another late-game GF with no stat junctions, but unlike, say, Tonberry, it's not a complete wild card, as Doomtrain has access to two very useful junctions - Elem-Defx4 and ST-Def-Jx4. Cerberus (junctioned to the Quezacotl user) gives ST-Def-Jx4, while Alexander (junctioned to the Ifrit user) gives Elem-Defx4, meanwhile the Shiva user has neither... ignoring the use of any Status Guard or Elem Guard items, of course. That being the case, Doomtrain goes to the Shiva user, ensuring they've got as many protective junctions as possible.
Again, barring the use of ability-teaching items, this should ensure the Quezacotl user has ST-Def-Jx4 (via Cerberus) while the Ifrit user has Elem-Defx4 (via Alexander). If you completed the sculptor's quest in the Shumi Village you'd have gained a Status Guard, which will bring the Ifrit user up to speed, and if you acquired the Selphie Card you can Card Mod it into three Elem Guards, which will protect the Quezacotl user. Suffice to say, now that you have Doomtrain there's a good chance all your characters will have the maximum possible Status Defense and Elemental Defense slots.
While the junction for Doomtrain was easy to figure out, there are more abilities at play. Doomtrain also has the Auto-Shell ability, which, like Auto-Haste, will permanently bestow the equipped character with Shell... provided Auto-Shell is equipped, of course. It's a potent ability that you should consider getting on more GFs when you get the opportunity to do so. Don't worry, we'll cross that bridge when the time comes.
Next - and perhaps most interesting is the Forbid Med-RF ability, which really deserves a discussion on its own.
Let's look at what can be refined with Doomtrain's Forbid Med-RF ability:
|Adamantine||5 = Vit Up x1|
|Aegis Amulet||2 = Spd Up x1|
|Doc's Code||1 = Megalixir x1|
|Elem Atk||1 = Elixir x4|
|Elem Guard||1 = Elixir x4|
|Gaea's Ring||1 = HP Up x1|
|Hundred Needles||1 = Spd Up x1|
|Hyper Wrist||10 = Str Up x1|
|Jet Engine||50 = Spd Up x1|
|Knight's Code||1 = Vit Up x1|
|Luck-J Scroll||1 = Luck Up x1|
|Magic Armlet||10 = Spr Up x1|
|Med Kit||1 = Megalixir x2|
|Mega-Potion||20 = Elixir x1|
|Monk's Code||1 = Str Up|
|Rocket Engine||5 = Spd Up x1|
|Royal Crown||10 = Mag Up x1|
|Shaman Stone||10 = Hero-Trial x1|
|Status Atk||1 = Elixir x4|
|Status Guard||1 = Elixir x4|
First, note that many recipes yield Elixirs, which are fine restoratives, but... some of the items required are rather rare. Mega-Potions and Remedy+ items are better bases for Elixir refinery, or better yet, the Angelo Card. Much more interesting are the stat-boosting items (HP Up, Str Up, etc.), most of which you can't do much with just yet, but Forbid Med-RF is one essential step to boosting several stats just by buying, selling and refining within menus... provided you've got the patience.
Now that you have Doomtrain - or at least have the key component you'll need to summon Doomtrain once you acquire the other, aforementioned items - it's time to move on to the Lunar Gate.