Source: http://www.outspark.com/forums/showthread.php?t=34582

The following is a list of all the boss/chief monsters found in Fiesta and their corresponding locations. Please update if needed:

King/Hero Mobs: [Spawn time: 6 Hours]
King Boogy (drops: Lvl15 Staff, Mace) [Location: Sea of Greed | Grid: F7]
Zombie Mutant (drops: Higher % of Green drops) [Location: Moonlight Tomb (E1), Vine Tomb (H8)]
Kebing's Dream (drops: Blessed/Lucky Stones T1) [Location: Burning Hill | Grid: B5]
King Werebear (drops: Blessed/Lucky Stones T2) [Location: Goblin Camp | Grid: B1]
Huge Greenky (drops: Higher % of Green drops) [Location: Ancient Elven Woods]
Giant Stonie (drops: Blessed/Lucky Stones T4) [Location: Forest of Slumber (F5), Concealed Prison 2 (??)]


Cave King Mobs: [Spawn time: 10 Minutes]
Lvl 20-36 cave: King Marlone (drops: all Lvl 20 weapons, KM ring, Purple Items Lvl 20/35)
Lvl 30-46 cave: Zombie King (drops: all Lvl 30 weapons, ZK ring, Purple Items Lvl 35)
Lvl 40-56 cave: Giant Goblin King (drops: all Lvl 40 weapons, GGK ring, Purple Items Lvl 35/55) [Location: Concealed Peak]
Lvl 50-66 cave: Torture King (drops: all Lvl 50 weapons, TK ring, Purple Items Lvl 55)
Lvl 60-76 cave: Giant Orc Captain (drops: all Lvl 60 weapons, GOC ring, Purple Items Lvl 55/75)
Lvl 70-86 cave: Giant Harpie (drops: all Lvl 70 weapons, Purple Items Lvl 75)
Lvl 80-96 cave: Guardian Master (drops: all Lvl 80 weapons, Purple Items Lvl 75/95)
Lvl 90-106 cave: Dungeon Caiman (drops: all Lvl 90 weapons, Blues 95) [Location: Tears Marsh - Level: 9x Dungeon]; Shadow Master Boss (drops: all Lvl 90 weapons) [Location: Temple of Spirit]

Chief Mobs: [Spawn time: 5 min]
Mara (drops: Mara's Ring) [Location: Sea of Greeds | Grid: D5]
Marlone (drops: Marlone's Ring) [Location: Burning Hill | Grid: D4/D5]
Were Robo (drops: Robo's Ring) [Location: Vine Tomb | Grid: C7]
Goblin King (drops: Goblin King's Ring) [Location: Goblin Camp | Grid: I2]
Legendary Tree (drops: ???) [Location: Ancient Elven Woods , Forest of Slumber]
Skeleton Knight (drops: ???) [Location: Luminous Stone 2]
Ghost Knight (drops: ???) [Location: Concealed Prison 2nd Floor]
Giant Magmaton (drops: ???) [Location: Burning Rock]
Cursed Knight Lord (drops: ???) [Location: Flaming Mine]

(Mini Boss) Elite Mobs: [Spawn time: Random]
Hero Slime (Lvl: 2) [Location: Forest of Tides]
Mushroom Fighter (Lvl: 4) [Location: Forest of Tides]
King Crab (Lvl: 8) [Location: Forest of Tides, Sand Beach]
Angry Wolf (Lvl: 11) [Location: Sand Beach]
Huge Phinoflie (Lvl: 13) [Location: Echo Cave | Grid: G3]
Ratman Fighter (Lvl: 15) [Location: Forest of Mist]
Sharp Boar (Lvl: 17) [Location: Forest of Mist]
Boogy Knight (Lvl: 17) [Location: Forest of Mist, Sea of Greed]
Cave Kebing (Lvl: 21) [Location: Luminous Stone 1]
Jewel Grave Robber (Lvl: 22) [Location: Luminous Stone 1]
Kebing Speeder (Lvl: 22) [Location: Sea of Greed, Burning Hill, Luminous Stone 1]
Piggy Bat (Lvl: 30) [Location: Moonlight Tomb]
Zombie Master (Lvl: 34) [Location: Moonlight Tomb]
Lamp ViVi (Lvl: 34) [Location: Moonlight Tomb]
Zombie Knight (Lvl: 35) [Location: Moonlight Tomb]
Ghost Slime (Lvl: 37) [Location: Moonlight Tomb | Grid: E5]
Hob Fighter (Lvl: 40) [Location: Vine Tomb]
Werebear Fighter (Lvl: 46) [Location: Goblin Camp]
Younger King Coll (Lvl: 51) [Location: Collapsed Prison]
Ogre (Lvl: 51) [Location: Collapsed Prison]
Older King Coll (Lvl: 52) [Location: Collapsed Prison | Grid: I6]
Elder King Coll (Lvl: 53) [Location: Collapsed Prison]
Karasian Arch Templer (Lvl: 59) [Location: Collapsed Prison]
Greenky Big (Lvl: 63) [Location: Ancient Elven Woods]
Queen Spider (Lvl: 63) [Location: Ancient Elven Woods, Concealed Prison 1st Floor]
Bright Golden Bat (Lvl: 64) [Location: Concealed Prison 1st Floor]
Nox Captain (Lvl: 64) [Location: Uruga, Concealed Prison 1st Floor, Ancient Elven Woods]
Ratman Elite Knight (Lvl: 65) [Location: Concealed Prison 1st Floor]
Giant Elven Tree (Lvl: 68) [Location: Ancient Elven Woods]
Flame Slyph (Lvl: 72) [Location: Forest of Slumber]
Blue Archon (Lvl: 75) [Location: Concealed Prison 2nd Floor, Forest of Slumber]
White Joker Trumpy (Lvl: 81) [Location: Forest of Slumber]
Guardian Master (Lvl: 91) [Location: Burning Rock]
Cursed Knight Gold (Lvl: 94) [Location: Flaming Mine]

KQ items:

Special Drop:
Pets - Can be mined or droped from mobs.
Rings/Necklaces - Can be mined or droped from mobs.

King Slime (Lvl 5-16)
Tier 1 Stones
Slime Earings
Pots
Level 15 weapons +2-6

Mara Pirates (Lvl 17-25):
Tier 1 Stones
Mara Earings
Pots
Level 20 weapons +2-6

Golden Hill (Lvl 20-32):
Tier 2 Stones
Gold/Jewel Earings
Pots
Level 30 weapons +2-6

Millenium Robo (Lvl 33-45):
Tier 2 Stones
Robo/Dark Earings
Pots
Level 40 weapons +2-6

Giant Honeying (Lvl 40-50):
Materials: Tier 3
Items: Pots, Stones

Mini Dragon (Lvl 46-60):
Materials: Mineable
Items: Pots, Weapons, Stones, Earings, Rings

Mini Dragon (hardcore)(Lvl 46-60):
Materials: Mineable
Items: Pots, Weapons, Stones, Earings, Rings, T3 Scrolls

Spider Assault (Lvl 60-70):
Materials Tier 3, 2-7 stacks of 30
Items: Pots, Stones, Scrolls

King Kong Phino (Lvl 70-79):
Materials Tier 3, 2-7 stacks of 50
Items: Pots, Stones, Scrolls

Gordon Master (Lvl 80-89):
Materials Tier 3, 2-7 stacks of 50
Items: Pots, Stones, Scrolls, Weapon

Rebelion War (Lvl 90-99):
Materials Tier 3/4, 2-7 stacks of 50
Items: Pots, Stones, Scrolls

PVP KQ (all of them)
1st: 1 50% exp card (1 hour), 1 50% War rant (1 hour), 1 random Purple
2nd: 1 50% exp card (1 hour)
3rd: 1 50% War Rant (1 hour)