I kinda forgot about this thread

(this is a subforum I don't really visit)
Hmm, well the diff system is best explained in one of the forum's threads, ... whoa. I don't have a topic that explains how exactly the diff system works o_O; Oops, I must fix that. In the meantime, a quote from the NPC that explains you the diff system in-game:
mes "@diff (for 'difficulty') is a very interesting command which affects the level of spawned monsters.";
mes "Each time someone walks into a dungeon, apart from the 'stock' enemies you find there, there's also a group of randomly spawned enemies. These enemies usually share the same characteristics of the stock ones.";
mes "Higher difficulty will mean higher level mobs. The level of these mobs depends both on the level of the normal enemies and the difficulty setting.";
mes "At minimum difficulty (1%) the passed level is 0, and thus the random mobs have half the level of the stock ones.";
mes "At maximum difficulty (100%) the passed level is twice your base level, and thus the spawned monsters will much harder.";
mes "There is much more to what the difficulty does... you should ask Glenn for the full details.";
And the long version:
mes "Difficulty? Alright... this is my favourite topic.";
next;
mes "["+@name$+"]";
mes "All that difficulty does is modify your base-level in mob selection and leveling processes. At min your level will be 0, at max, it'll be twice your level. Why is that useful? Because your adjusted level is used to calculate the map's difficulty.";
mes "The 'map difficulty' is the level of the mobs on a map. A map can be said to have two different difficulty levels: Stock and adjusted. The stock difficulty is the average level of the mobs that you'd normally find in a map. This is the intrinsic difficulty of a map. The adjusted difficulty is the average between the map's stock difficulty and the average level of players in that map.";
mes "The adjusted map difficulty has two effects:";
mes "- All mobs that have less level than the adjusted map difficulty will level up to that level.";
mes "- There will be additional mobs that are randomly selected to spawn in the current map. They will share similar properties of the stock mobs, such as element and race, and will be of a level similar to the adjusted.";
mes "When the difficulty of a map changes (by leveling, players entering/leaving the map or using @diff) it will take a few kills before the new difficulty triggers. Getting killed also speeds up the process by which the map's difficulty changes. However, only mobs that are not in the sight of any players will have their level changed.";
next;
mes "["+@name$+"]";
mes "Your personal difficulty also has two additional side effects:";
mes "Aggressive mobs will ignore players of lower level unless their difficulty is higher. Likewise, mobs of lower level will ignore players who use low difficulty. However, this only applies for as long as the monster is undamaged and no other party members use higher difficulty. A non-provoked monster will also become provoked if a monster of similar level requests help.";
mes "The exact difficulty at which an aggressive mob will ignore you is 'Monster LV + 25 - Player LV', note that this will not work on GvG/WoE related maps, where all monsters will always be in 'provoked' state.";
mes "If you kill a monster much lower level than yourself, their drop rate will suffer unless you raise your difficulty. This effect is meant to nullify the benefits of 'farming' a weak monster. To prevent this, always make sure your difficulty is set to at least 'Player LV - 25 - Monster LV'";
next;
mes "["+@name$+"]";
mes "Finally, some general information about the command:";
mes "- Your difficulty setting is stored among sessions.";
mes "- Using @diff without an argument displays the current monster levels in the map. If the map has no monsters, it will just display your adjusted base level.";
mes "- You can use low difficulty temporarily if you want to sneak through high level aggressive mobs without them attacking you.";
mes "And that is it. Remember that the secret to a great challenge that is neither frustrating nor boring is to select the appropriate difficulty.";
I will probably quote this (minus the npc code) as the thread that explains difficulty in the forums.
Easy mobs that get leveled up are not easy exp because the skill levels they use also go up as well, and their base stats and HP go up following the original mob's build and taking into account the aggregate stat information of all other mobs (meaning that a Lv130 poring will have as many stat points and HP as most monsters that are normally level 130 with around the same vit). Since all mobs get random skills, they are not hopelessly easy as most standard RO monsters are neither (ie: they just have normal attack and a few crappy skills).
Probably the largest drawback of MouRO is that, as an ever evolving server, it has accumulated a long list of changes throughout the years, and this in turn means a steep learning curve for new players. Fortunately many of the current players are eager to help through any new players, and the new memory rollback system makes it a lot easier for veterans to help out lower level people without having to leech them in high level areas where they are helpless otherwise.