So, today, JMS got the "Hard Core" mode that EMS got in the form of the "Supreme" world earlier this year. There are noticeable differences so far, from the rules to in-game elements. If GMS is to get this content, I'm sure whatever JMS has done to it, or will do to it, will be the version GMS would get.
These are the rules :
※To enter the Ibara world, you will receive a quest on characters only level 150 or higher in the normal servers.
※You may not create new characters (You may also not use Character Cards).
※You may only transfer up to 3 characters to the Ibara world. To move more than 3, you will need to purchase character expansion slots.
※Characters in the Ibara world will start from level 1.
※All characters transferred to the Ibara world will become Adventurers.
※If you transfer your character to the Ibara world, your original character will not disappear.
※When you transfer to the Ibara world, you will not be able to delete your original character nor your transferred character.
※The MTS will not be accessible in the Ibara world.
※The "Ever revolving destiny" quest is targeted at characters at levels 10 to 60. (I have no idea what this quest is... When I find out, I'll explain it.)
※You will not be able to purchase the following items in the Ibara world.
・World Transfer Ticket
・Character Card (Level 50/100)
・Cubes other than Miracle Cubes
・All kinds of Familiar Booster Packs
・All kinds of Friendship Rings
・All kinds of Couple Rings
Those are the rules/information listed in the patch info post.
As far as in-game content goes, I'm still exploring everything (I've still not made it out of the tutorial, due to the fact that the game is still under an emergency maintenance at the time of me posting this), but from what I can see so far, mobs deal less damage than their EMS counterpart.
From what I remember, the ones in EMS were doing 50+ damage (or even 100+) and players were dropping like flies. This, however, may only apply to tutorial mobs. When I get a chance to explore more of the server, I will post more information about what I find.