Im making this topic because im looking for those monsters but i relly cant find them.Please if you know where are they tell me.
Hades
 Persephone
 Hecate
 Cerberus
 Styx
 Cocytus
 Pyriphlegethon
 Thanatos
 Lethe
 Abysmal Infernal
 
The Above mobs are part of an underworld gauntlet and was accidentally wiped last year, I intend to bring it back, just need time:)

  Crimson Dragon Stygian Abyss
 Moon Dragon Removed
Gargantis Boss in Sanctary
Navery Underworld
Dragon of the Flame
 Jack Frost - Boss in Prism of Light
Blackthorn's Incarnation Ilsh, Blackthorn/Juka castle
 Caribos - Valor in hut

Most of these I haven't heard of, much less seen...but i'll take a stab

Ceberus - big Cu looking mob at the tail end of TerMur underworld past Stygian Dragon

Abysmal Infernal - Cross between a blob and octopus that ordinarily hangs in Gauntlet rm #5.  Also stage 4 of a tough champ where Dante has been holding the events lately.  He prob removed it cuz the location is perfect for the 3n1 champ events we have been having, unless I'm completely mistaken, in which case, idk 

Gargantis - new mob boss, custom, part of the peerless quest.  He is the boss you defeat in Sanctuary.  This would also be the Gargoyle Underboss, maybe perhaps.  Where did these terms come from?

Navery - big spider, located by dropping in a hole in TerMur underworld topside.  Can show you, but uh, take a crew

The dragons - We have the colored dragons, part of the quest to obtain an Evo egg, the semi-precious gem dragons.  I only know of two others:  Stygian Dragon who is in TerMur in his temple and the Dracolich, located in Khaldun.  I suspect one of those is the Moon Dragon or Dragon of the Flame you refer to, but ? (where'd did you get those terms?)  There are also new dragon mobs in Sanctuary, that might be the Dragon of the Flame you refer to...

that's all I got

On note of the Dragons.

Dragon of the Flame - no longer a spawned mob in game. Talisman of Flame Drops on the Stygian Dragon
Dragon of the Moon - same as Dragon of the Flame
Dragon Infernal - Used to spawn where Navery does now. Has not been confirmed if its still in game or not.

Regarding the Flame and Moon Talis, I was told that Dracolich (big dragon) in Khaldun has a 1% chance to drop 1 of 10 different items including the Flame and Moon Talis.... I have killed him LOTS of times but no cool drop yet 
Yes this can drop the flame and moon talys