As you and your Asmodian wings approach the level 30 milestone, a new quest will pop up in your journal: [Group] The Three Keys. This little gem, once completed, will grant you access to the Fire Temple. This instance, in western Mt. Musphel near the Sky Temple of Arkanis, is sort of misleadingly named, as it has more in common with a hole in the ground (commonly referred to as cave) than it does with a temple. Although, there are some ruins strewn about the place which would lead one to believe it may at some point in its history been a temple. Now, though, it is home to fiery fire elementals, rocky rock elementals, gargy gargoyles, and one sexy lady by the name of Kromede.
Before you can begin your fantastic journey into this temple/cave you must first complete the aforementioned group quest inside the Sky Temple of Arkanis. For the most part, this quest is trickier than the instance that follows. For its completion, you must go through three element themed mini instances of increasing difficulty, or decreasing difficulty, or even random difficulty--depending on which order you do them in. The three elements the rooms are themed after are wind, which is easiest, followed by water, then finally fire is the hardest; each room has an assortment of monsters that match its respective element. These rooms are built in a similar manner and each requires you to glide heroically from floating platform to floating platform. You must be extremely cautious of monster paths and spawns when landing (and be sufficient enough at gliding) or you'll end up in a bad state.
Once you've attained the final key to this wonderful little group quest you can turn in all three keys to your friendly neighborhood fire elemental that gave you the quest. He will then give you the next quest in the line: The Captive Flame, for the Fire Temple. It should be noted that while The Three Keys can be completed by level 28, the Fire Temple's monsters are 33-37. So, while the instance itself isn't too difficult, you may not want to consider doing it until roughly 32--maybe 30 or 31 if you're feeling ballsy, or have the luxury of being a healer who doesn't have to worry about hitting high leveled monsters. As for class makeup, since it is a pretty easy instance, you can probably throw whatever at it and be just fine, I ran it for a few hours one night with a spear wielding gladiator tanking. Just like anything with elite monsters, sorcerers for crowd control are highly recommended.
This instance has six random spawning bosses; it's fairly unlikely to find them all up in one clear, though not impossible. You can expect to find one or two up in any given run. Three of these random spawning bosses are along the main path taken through the instance so you should be able to kill them with minimal clearing. The other three are well off the beaten path and, for the most part, completely ignored by most groups. In fact, I've never actually killed any of the three bosses that would require significant clearing to even see if they're spawned.
Experience rewards aren't great by any standards, but Kromede, the final boss, does drop some great gold (unique) items, though they are rather rare. She actually comes in two flavors, the most common version, Kromede the Corrupt, is a bit easier than her harder counterpart, Vile Judge Kromede. It is believed by some that Vile Judge is more likely to drop the unique items. Though, the only time I saw one drop (out of 40 or so runs) was from a corrupted Kromede. The random spawns also have a chance to drop decent level 35 greens, though most of the time they drop next to nothing.
Because of its 30 minute reset timer and quick boss runs, many people are likely to milk Fire Temple for all it's worth and repeat it for hours on end. These speed runs take the path of least resistance, skipping monsters and gliding once or two. For anyone interested in fast clears, it's most common to first run down the center of the first room and pull the far right pack of fire elementals into the corner and kill it there. Once they're dead, go down the only hallway, killing what you need to. At the end of this hallway is a stone ledge you can climb up and glide from, skipping two or three pulls this way. The first named monster you'll encounter, Silver Blade Rotan, patrols up and down this hallway if it's up. After you've dispatched a pair of kalgolems, you can either choose to go left towards the last boss, or straight to more kalgolems to see if a second rare spawns is up.
You'll begin to encounter gargoyles when you continue toward Kromede, at the end of this hall though, is the next rare spawn, a mudgolem, you may or may not run into, Tough Sipus. This room with four paths out is pretty dense and has some exciting gargoyle patrols, so it's advisable to mind your step in here, or you'll be zerged by the entire cast of Gargoyles. If Tough Sipus is too scared to come and play, then you have a decision of which way to go on your hands. Straight ahead is Chalice Guard Denlavis, the monster required for "A Captive Flame"; a quest is rather exciting to do with everyone in the group, as it requires a slew of clicking random chalices to discover which is the right one, be sure not to drink from any of the unholy grails or you may end up a pile of dust.
To the left are a couple of rare spawns, so chances are you'll never see this area of the instance like me. To the right though, is the last rare spawn, Broken Wing Kutisen, and Kromede! The rare spawn is in the room just to the right with a bunch of gargoyles; you'll see him in the back of the room, intact wings and all. If he's not there, you can just skip that room entirely.
This brings us to Kromede up ahead in the next room, in an area of the instance that resembles a temple in any regard. Every time I've run through Fire Temple, I always keep to the right and skip the center monsters all together. She's standing in the back of the room next to a talking mirror. I'm not exactly sure of the purpose of this mirror; I assume it was for a quest I skipped. But, since I was already aware I was the fairest of them all, I opted not to strike up a conversation with it.
The fight with Kromede is pretty simple, although Vile Judge Kromede is a little tougher--nothing insurmountable though. For ranged classes, you can basically just stand back and shoot or cast. She does this short ranger aoe that melee can run out for, I never thought that this was very necessary, you can probably just pop a health pot and be okay.
Chances are, by the time you get to 40, you'll be pretty burned out on Fire Temple, and if you're lucky you'll have gotten yourself a gold weapon by then. In all likelihood you'll only see one or two gold items, and they probably won't be the one for your class. So, don't get your hopes up! All in all, though, Fire Temple is a pretty drab and uninteresting instance, and I'm sure that the only reason most people will have to go through it more than once is the allure of awesome loot, which is obviously more than enough incentive.