Obtaining the Trident of the Red Rooster is one of the most difficult and arduous feats in the entire game. It takes considerable time and effort as well as careful planning, spread throughout the game.
Possible tactics for retrieving an AoLS at this point of the game include wishing. Common methods of obtaining a wish include gremlin bombing (versions prior to v.1.2.0, only) extensive grave robbing or pool-sipping. A large number of pools can be found in the Darkforge. Saving Khelavaster grants, among other things, a reward of six scrolls of corruption removal, which will be extremely helpful in the latter parts of the quest. The lawful boost for saving him may be one to look out for.
After saving Khelavaster, the player must successfully navigate to the bottom of the Caverns of Chaos to reach the Unreal Cave System and kill Srraxxarrakex for Sharad-Waador. This is quite a task even for high level players, as it requires traveling through the dangerous Blue Dragon Caves and killing a very powerful wyrm.
Assuming that the previous task is accomplished, the player must then achieve character level 45 (if not already) and visit the Assassins' Guild to receive the Kill Filk quest from the assassin prince.
The difficulty of the quest is heavily dependent on a relatively obscure parameter: the type of the monster the PC had killed first upon arriving in the Drakalor Chain. Filk can be found on the level of the Infinite Dungeon that matches the number of monsters the PC has killed of the same type as their first (e.g., if the first kill was a large bat and the PC had subsequently killed 60 more large bats, Filk will be found on level 60 of the dungeon).
Thus, if the player was conscious of the first kill significance and chose a rare monster (for example, a beggar, which can only be found in Lawenilothehl), Filk can be easily reached. If, however, the first kill was a common monster (a rat, an orc, a kobold, etc.) the player will likely have to make a long trip. Note that no special message is given when the PC enters the level where Filk resides, which may complicate the quest progression if the player does not remember the first kill. If the PC leaves the level while Filk is still alive, it will not be possible to find him in the Infinite Dungeon afterwards.
If Filk was neutral towards the PC when the PC left the level, it is possible to meet him wandering around the wilderness. If Filk was hostile when the PC left the level, the player will not be able to complete the quest at all.
Filk is extremely fast—the fastest monster in the game—and also has the highest DV in the game. However, as with all quicklings, he has very few HP. Players are advised to use some form of unavoidable damage (any ball spell, Burning Hands, crystals of fire, offensive alchemy, wands of fireballs). Typically, using any of these methods will reliably kill him in one hit.
The reward for the quest, the location of the Scintillating Cave, is received directly from the Mad minstrel, not the assassin prince. In fact, the player may wish to kill the assassin prince immediately after receiving the quest to obtain the artifact dagger Sting.
The Emperor Moloch
The bottom level of the Scintillating Cave, a dangerous place in itself, is the home of the Emperor Moloch, an extremely slow, but also extremely strong adversary. Unlike Filk, he has almost zero DV, while having the highest PV in the game. As such, it is recommended you use attacks that either bypass PV entirely (phase daggers or a weapon of penetration) or deal enough damage to get past it (such as blessed arrows or quarrels of demon slaying).
The Emperor Moloch will drop the crumpled scroll, which can then be taken to Khelavaster, who by now has returned to the small town of Terinyo. If a lawful or neutral player gives him the crumpled scroll, he will summon for them the legendary Trident. Don't do it while chaotic!
The scroll may not be wished for and if it lost during transit, the PC will be unable to receive the trident. However, it is possible to read the scroll without making it disappear. Doing so allows the PC to use a magical writing set to write a replacement in case the original item was destroyed. Players are, therefore, advised to read the scroll as soon as it is picked up (this action will take only one turn) to avoid drastic potential consequences.