This is based on Nolan001's idea "Sultan's Palace idea."
KINGSISLE:
I think that is actually an incredibly good idea. I wonder why I did not think of that sooner. Allow players to duel select monsters and bosses in their dueling circle. It would prevent travel, and entering/exiting out of dungeons to reset them, just to fight certain bosses again.
This would also accomplish a certain issue many legendaries are having: boredom. Eventually, I realize everyone will get bored, but this would most certainly delay it, and keep players entertained for a good while longer.
This is also an idea that you could help increase your crown sales. Since only select castles have dueling rings, you can sell a dueling ring for crowns in the crown shop. Also, select orbs could also be sold at the crown shop, perhaps generating more crown sales. (Those respective monster's orbs would of course have a very low drop rate.)
Now, the fun part, collect them all! Monsters and select bosses would drop 'orbs.' Those orbs would not be a 100% drop, and drop rate would change according to how 'rare' that monster/boss is. This orb would act as a key item, instead of being a physical object using up inventory space.
Once that orb has been found, it would automatically unlock it for battle in the castle's dueling ring. Bosses such as Yukai (I believe that is spelled correctly) would have a low orb drop rate, since that boss is never pointed out, and 'hidden.' Monsters such as a wandering troll would have a fairly high drop rate (although one should still have to work for it) since it is such a common monster.
Bosses that come from special dungeons like Waterworks or Helephant, etc, would of course not drop orbs, they could only be fought by actually completing the dungeon. The Stormriven column bosses, or Kraken boss from Triton avenue (spawned bosses in general), would also drop orbs. Since you could spawn and fight those indefinitely anyway.
Having those 'key items' players could teleport home to their castle, and have those monsters and bosses unlocked. Their could be a little pull up menu or a list given to you by a dueling ring referee (or some NPC or furniture item attached to the dueling ring) with monsters and bosses corresponding to which area was selected.
The menu could look something like this. Each individual world would be displayed. Player selects that world, and each individual area within the world would be displayed. Like, Wizard City > Unicorn Way, Triton Avenue, Firecat Alley, Colossus Blvd, Olde Town (bosses), Sunken City. Then, upon selecting an area, the corresponding monsters would be listed and bosses. Bosses could be highlighted in a different color, or annotated accordingly as to identify that they are bosses.
Something new for you guys to think on. Hope you have fun playing with that idea. I think that is a really great one. Would keep players busy with hunting for a long time, and enjoy their castle even more than ever.
