This is a copy from the VG main forums:
Since mobs which drop platinum faction coins are relatively rare we could make a list of where to find them. Lets include all levels.
Mobs known to drop coins:
LEVELS 0-19:
RHAATHUL THE CORRUPTER (3-dot, 8 mob in Ksaravi Hollow in Khal in Qalia)
SULUDYN (3-dot, 10 mob in Serpent of Sihari in Lomshir in Qalia
MASTER UIZA-DO KAHN (3-dot, 10 mob in Ra'Jin Stronghold in Kojan)
FOREMAN SNARLBACK (4-dot, 11 mob in Orcbane Mines in Vault of Heroes in Thestra)
XAOXIN (4-dot, 11 mob in Riftseeker's Torrent in Thestra)
XATHOK (4-dot, 12 mob in Riftseeker's Torrent in Thestra)
KAON BROODMOTHER (3-dot 11-13 mob in Arcanium in Leth Nurae in Thestra)
LALEN FRAE (2-dot, 15 mob in Veskal's Exchange. Pops after completion of "The Cure" quest series)
CLAN CHIEF BARGORG (2-dot, 19 mob in Stonecrushers Enclave in Three Rivers in Thestra)
KING JURDIN THUNDERAXE (5-dot, 19 mob in Khegors End in Thestra)
LEVELS 20-29:
ELBARION (5-dot, 21 mob in Fallen Lyceum sky part in Kaon's Rush in Thestra)
AMONIR (5-dot, 21 mob in Fallen Lyceum sky part in Kaon's Rush in Thestra)
MORWAEN (4-dot, 21 mob in Fallen Lyceum sky part in Kaon's Rush in Thestra)
Kalendra the Dark Witch (5-dot, 22 mob in Kalendra's Coven in Skrillien Point in Qalia)
OVERKING BARRAK (5-dot, 23 mob in Rekk hobgoblin valley in Renton Keep in Thestra)
GRAND TYRANT MILAS (5-dot, 24 mob in Ksaravi Gulch in Qalia)
RUL'ALOUK THE SOULSCORCHER (5-dot, 24 mob in Imanjal Sacellum in Skrillien Point in Qalia)
Mistress Anaya (4-dot, 24 mob in Hillsbury Manor in Misthaven Crossing in Thestra. Last part of questline there)
Mistress Bella (4-dot, 24 mob in Hillsbury Manor in Misthaven Crossing in Thestra. Last part of questline there)
Mistress Raylia (4-dot, 24 mob in Hillsbury Manor in Misthaven Crossing in Thestra. Last part of questline there)
Kill Kronus in CIS and 3 adds pop. Each one is 2-dot, 28-29 mob and can drop coins
Ageless One (x-dot, xx mob in CIS in Qalia) (need better information)
QUEEN AYXLXYX (5-dot, 26 mob in Ant Mound in Renton Keep)
VELETHEZOK (5-dot, 25/26 mob in Skrawlra Rock in Qalia. Needs to be summoned by collecting 3 different color masks)
LEVELS 30-39:
Nishek (6-dot(?), 31 or 32 mob in Trengal Keep in Thestra. Summoned, need whip from TK6)
THURRE (5-dot, 34 mob in Zossyr Hakrel in Qalia)
ZYFUUR (5-dot, 35 mob in Cragwind Ridge in Qalia)
GORLASH TOXIL (5-dot, 37 mob in Dargun's Tomb in Thestra)
BAHAR'NIHAB THE REAPER (6-dot, 37 mob in Fields of Despair in Thestra)
SOLATHUS (6-dot, 38 mob in Ruins of Vol Tuniel on Thestra)
YALSYL VONALYS (6-dot, 38 mob in Thelaseen in Thestra)
HIGHLORD SHO'DAR (5-dot, 38 mob in Thelaseen in Thestra)
MYRION THE PURE (5-dot, 38 mob in Spires Keep in Thestra)
LEVELS 40-49:
HIGH COMMANDER RAKH'YOR (6-dot, 40(?) in Greystone in Thestra) (exact level needed)
HRUK (6-dot, 40 mob in Karrus Hakrel in Qalia)
TAJIIHOSK (6-dot, 41 mob in Karrus Hakrel in Qalia)
OBSIDERRU (6-dot 40ish summoned mob in Karrus Hakrel in Qalia. Needs 30 aqual orbs for summon) (exact level needed)
DRILLLZARAX (6-dot, 41 mob in Islands of Madness in Qalia. Mob pops in tower)
HIGH TORMENTOR ZERAXEZ (6-dot, 42 mob in Vi'rak lair in Thestra(?))
XAALESEESH THE INFERNO (6-dot, 42 mob in Vi'rak lair in Thestra(?))
Overwarden Ehu Dal (6-dot, 44 mob in Sunset Pointe in Qalia)
Warlord Khurang (6-dot, 44 mob in Sunset Pointe in Qalia
Father Xennu (6-dot, 45 mob in Mind's Crown in Qalia)
Naxxillar (4-dot, 45 mob in Mind's Crown in Qalia)
Exxilar (4-dot, 45 mob in Mind's Crown in Qalia)
Araxxishar (4-dot, 45 mob in Mind's Crown in Qalia)
LEVELS 50+:
Majordomo in RI in Qalia (dot + other info needed)
Warlord in RI in Qalia (dot + other info needed)
ALUUL (6-dot, 53 mob in RI in Qalia)
DJUUL (6-dot, 53 mob in RI in Qalia)
SHALUU (6-dot, 53 mob in RI in Qalia)
KHORR (6-dot, 53 mob in RI in Qalia)
Hegnerian in swamps in Thestra (dot + other info needed)
King Mnalus (6-dot, 50 mob in swamps in Thestra)
LORD FALADRIEL (6-dot, 50 or 53 mob in Flordiel, Thestra)
Queen Vixxaeva in swamps in Thestra (dot + other info needed)
PHAROAH SHEKHAN NKOSA (5-dot, 51 mob in Nusibe Necropolis in Qalia)
Godking (x-dot, xx mob in Nusibe Necropolis in Qalia) (dot + other info needed)
Nepherit (6-dot, 50 mob in TOT temple before flip in Qalia)
............ 50=6 dot last of the flipped names in TOT in Qalia (name needed)
RAFFEN (6-dot, 53 mob in Old Targonor in Thestra)
AKANDE (6-dot, 53 mob in Old Targonor in Thestra)
SHORUL (6-dot, 53 mob in Old Targonor in Thestra)
CENNFAR (6-dot, 53 mob in Old Targonor in Thestra)
NARANDA (6-dot, 53 mob in Old Targonor in Thestra)
TEKAR (6-dot, 53 mob in Old Targonor in Thestra)
CHATH + his pet (6-dot, 53 mob in Heroes Plain in Thestra)
SHADOW (6-dot, 53 mob in Isle of Shadows in Thestra)
SYD (6-dot, 53 mob in SOuthern Stonepie Ridge in Thestra)
STRIFE (6-dot, 53 mob in Ridge of Memories in Thestra)
TISHRA (6-dot, 53 mob in Gorgalok in Thestra)
Kronax (x-dot, xx mob in Umyebum Crypt in ToT in Qalia) (dot + info needed)
I will comment on the level 21 nameds in the Fallen Lyceum. This place is easily accessed with a rented flying mount at Kaon's Rush. Fly far above the little floating island and decrease your altitude until the griphon breaks. This will put you right on top of the big dome, from there run off the side and following the top balcony until you see a door. Through the door and off the ramp there are 3 doors. Each door leads to a capped named that has an approximate respawn of 5 minutes. This means 3 capped nameds with respawn of 5 minutes each drop 1-4 plat coins and you can basically chain farm them. I've gotten about 200 coins so far in a couple days of playing casually with my cleric bot and I.
Great way to farm plat coins for the alts
