- MVP: This monster is usually stronger and summon slaves.
- Looter: This monster will take items on the ground. When it is killed, the looted item will be dropped.
- Assist: This monster will assist other monsters of its kind by attacking the person the others are already attacking.
- Aggressive: This monster will begin to attack people once they are in its range of sight.
- Changes Target: This monster will change its current target under certain conditions.
- Cast Sensor: This monster will immediately target a player who is casting a skill on it.
- Detector: This monster can still attack people who are hidden using Hiding, Cloaking, and Stalk.
- Immovable: This monster cannot move unless it is forced to move by a skill (e.g. Jupitel Thunder).
- Non-attacker: This monster does not attack.
- DemiHuman: Usually, notably, humanoid in appearance or behavior. Includes Player characters.
- Brute: Usually, notably, animalistic in appearance or behavior.
- Insect: Usually, notably, bug-like in appearance or behavior.
- Fish: Water element creatures who mostly reside in water themed fields or dungeons.
- Dragon: Usually, notably, reptile-like in appearance or behavior.
- Plant: Garden and woodland variety creatures.
- Formless: Creatures hard to categorize into other races, or have no form.
- Angel: A rare race that are mostly Minibosses with notable angel wings.
- Demon: Usually, notably, demonic in appearance or behavior.
- Undead: Creatures associated with the dead.
- Neutral: The basic elemental property, a large portion monsters are Neutral property. Neutral has no elemental weakness and resists the Ghost property, which also resists the Neutral property.
- Water: Water is the opposite of Wind. The Water property is the strongest against the Fire property, and the weakest to the Wind property.
- Earth: Earth is the opposite of Fire. The Earth property is the strongest against the Wind property, and the weakest to the Fire property.
- Fire: Fire is the opposite of Earth. The Fire property is very strong against the Undead property, is the strongest against the Earth property, and the weakest to the Water property.
- Wind: Wind is the opposite of Water. The Wind property is the strongest against the Water property, and the weakest against the Earth property.
- Poison: Poison property is slightly strong against the low level Fire, Wind and Earth properties, and is slightly weak to the Holy property.
- Holy: Holy is the opposite of Shadow. The Holy property resists many properties, is weak to the Shadow property, is also strong against it, and is the strongest against the Undead property.
- Shadow: Shadow is the opposite of Holy, and is the strongest against it.
- Ghost: The immaterial elemental property. The Ghost property resists and nullifies the Neutral property, is strong against the Undead property, and is only weak to itself.
- Undead: The Undead property absorbs the Poison and Shadow properties, is strong against the Holy property, and it is immune to itself. However, it cannot harm the Shadow property, is weak to the Fire and Water properties, and is also the weakest to the Holy property.
Some melee attacks of monsters have no element and are completely unaffected by elemental modifiers. Such attacks are referred to as being non-elemental. They have only a defending element, but can inflict elemental attacks using skills.
There are three sizes to monsters, Small, Medium, and Large. They are usually very noticeably one size or another. Adopted players are considered small, normal players are medium, and Pecopeco riders are usually considered large in PVP environments.
JellyRO Exclusive Monsters
The majority of these are event only monsters.
- Clueless Festive Orc
- Evil Easter Eggs
- Pax Imperia Minions
- Rekenber Minions
- Very Evil Easter Eggs
Spawn or drops rates differ in some way from the scripts found at the general RO database RateMyServer.
- Arcadia (gon_dun03) Wraith Deads added. Incubus Added.
- Einbroch Field (ein_fild08) Metalings increased.
- Fortress Saint-Darmain (cmd_fild06) Stem Worms added.
- Geffen Dungeon F1 (gef_dun00) Hunter Fly removed. Poporing increased. Poison Spores increased.
- Geffen Dungeon F4 (gef_dun03) Wraith removed. Wraith Dead removed. Wind Ghost removed. Hellion Revenant removed. Doppelganger added. Lord of Death added. Dark Lord added. Baphomet added. Baphomet Jr. added.Deviruchi added. Mini Demon added. Violy added. Incubus added. Succubus added. Dark Priest added. Bloody Knight added. Gremlin added. Alice added. Khalitzburg added. Abysmal Knight added.
- Glast Heim Underprison (gl_prison) Mobs increased. Rybios removed. Skeleton Prisoners added.
- Glast Heim Churchyard (gl_chyard) Mobs increased.
- Kokomo Beach (cmd_fild02) Mobsters increased.
- Lutie Field (xmas_fild01) Garm Baby increased
- Skellington, A Solitary Village (nif_fild01) Mobs increased.
- Sphinx F5 (in_sphinx5) Anubis increased.
- Suei Long Gon (lou_dun03) Gajomart added.
- Toy Monitoring Room (xmas_dun2) Myst Cases increased.
- West Orc Village (gef_fild14) High Orcs increased.
- Miyabi Doll spawn rate has been increased in ama_dun01 to 100.
- ve_fild07 now spawns 1.5x more mobs.
- Gajomart spawn rate in gld_dun01 has been increased to 20
- Elder in Clock Tower F2 and F4 were increased to 10 each
- The spawn rate of Obeaune has been increased.
- Guardian Stone (1907) - Changed to Formless/Ghost. HP Increased.
- Guardian Stone (1908) - Changed to Formless/Ghost. HP Increased.
- Barricade - Changed to Formless/Ghost. HP Increased.
- Roween (1794 - ie. galion's slaves) give experience
- Antonio Drop rates are different
Green marks a higher drop rate. Red marks a lower drop rate.
|Amon Ra||Krieg Dagger  (3%)|
|Agav||Holy Dagger  (0.03%)|
|Aliza||Rosary  (0.03%)|
|Abysmal Knight||Blade of Darkness (3%)|
|Bow Guardian||Sniping Suit  (0.06%)|
|Beelzebub||Ledger of Death  (0.03%)|
|Deviling||Blade of Darkness (15%)|
|Dullahan||Eye of Dullahan  (3%)|
|Echio||Holy Dagger  (0.3%)|
|Eddga||Krieg Dagger  (0%)|
|Iara||Necklace  (0.03%)|
|Fallen Bishop Hibram||Memory Book  (3%)|
|Fake Angel||False Angel Wing (100%)|
|Maya||Mother's Nightmare (0.9%)|
|Naght Sieger||Twin Edge of Naght Sieger (B)  (50%), Twin Edge of Naght Sieger (R)  (50%)|
|Nidhoggr's Shadow||Proxy Skin Fragment  (15%)|
|Obeaune||Necklace  (0.03%)|
|Orc Hero||Weihna  (3%)|
|Orc Lady||Earring  (0.03%)|
|Phreeoni||Weihna  (0%)|
|Satan Morroc||Diabolus Armor  (50%), Diabolus Robe  (50%), Diabolus Boots  (50%), Dark Bacilium  (45%)|
|Valkyrie Randgris||Valhalla's Flower (75%) , Valkyrie's Armor  (6%), Valkyrie's Manteau  (6%), Valkyrie's Shield  (6%), Valkyrie's Shoes  (6%)|
|Wounded Satan Morroc||Diabolus Armor  (30%), Diabolus Robe  (30%), Diabolus Boots  (30%), Dark Bacilium  (30%)|
- lh4 drops
- The weapon Executioner now drops from the monster Executioner.
- Book drop rate for Elder has been slightly increased.
Quote from: http://www.anesisro.com/forums/index.php?topic=120457.0 (15 may 2013)
|Alice||Alice Doll  (0.09%)|
|Bacsojin||Zaha Doll Hat  (3%)|
|Draco Egg||Baby Dragon Hat  (0.3%)|
|Evil Snake Lord||Evil Snake Lord Hat  (6%)|
|Fake Angel||Angel Blessing  (0.09%)|
|Explosion||Torch Cap  (0.09%)|
|Fur Seal||Seal Hat  (0.09%)|
|Geographer||Decorative Geographer  (0.09%)|
|Hyegun||Hyegun Hat  (0.09%)|
|Karakasa||Umbrella Hat  (0.3%)|
|Lady Tanee||Tanigumi Girl Doll  (6%)|
|Necromancer||Necromancer Hood  (6%)|
|Solace||Little Angel Doll  (0.3%)|
|Wood Goblin||Nest Hat  (0.09%)|
Silver Ring no longer drops from Succubus.