I got all Models from this Videos, including their Animation.
Now back to my Idea which I wanted to do.
Throughout the World Map you will have a Chance to encounter one of these "Unique" Monsters. They're hidden anywhere, Spawn Chance is low as hell so they are rare.
Once a Unique Spawns a Notice will appear : "A unknown Entity has arisen, be careful.". This is for the outside Map.
For the Dungeon Part the Notice would be : "A unknown Entity has arisen in a Catacomb".
For the Outside Map, those Uniques have a scripted Route that means they will follow their own Path, once they reached the End of it, they will simply disappear with the following Notice : "You can't feel the Power of the Entity."
The same goes for the Dungeon Notices.
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Once you have defeated the Unique / Entity, you may have the chance to tame it with a "Tamer" Skill. The Success Rate would be around 3-5%, once you have Tamed it, you will have your own Stone inside of your Inventory.
The Stone can be used twice a Day (Apply the Cooldown of Devil Spirit as example since it won't reset once you relog).
Once Summoned, you will enter the Berserk Mode, instead of getting the doubled Damage Power you will get hit by twice the Damage. The Color of the Berserk varies with each Summon, it resembles their Powers/Art. The Summon lasts for only two Minutes.
Each Unique/Entity has a Special Attack which the Summon will use immediately before time runs out, this Special Attack could lead to mass Destruction on the Battlefield or it may give Positive / Negative Effects on your Mates / Enemies.
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Twelve Entities and the God of those Entities is unknown, may it spawn once those Twelve Entities has been slayed?
Seven are located outside while Five are located in Dungeons. Once defeated, the true Entity will appear and has a Time Limit, if successful slayed Chances are 1% to gain this Type. It would be the strongest of all types that's why the Chance is low.
Every Entity has it's own Strength and Weaknesses, some are Healing Types, some are Tank Types, some are the Damage Dealer Type or some resemble the Death itself.
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To obtain a Entity in a Cave, you need to do a Questline which resembles the Entity itself, telling a huge Story about it, how it was born, how it was raised, how it became such a Monster and why it does even exist.
At the end of the Questline you will get a "Key to the secret Chamber" though, slaying the Entity alone is not possible.