Diamond is used for many things such as for construct, buying items etc. Midas , florens are used for promotion.
The following is how to get diamonds in the rossum mirror game.
Daily Quest
Daily Quest are carried out every day. Many prizes can be obtained including diamonds, tokens, florens etc.
Main Quest
The prizes from the main mission are almost similar to daily but the main mission can only be done once.
AFK income
AFK income allows players to get a lot of EXP, florens, evo capsules, gear, time scroll and other items without the need to log in. The farther the dungeon (chapter) is completed, the afk income will get more and better.
Starter project
The starter project lasts only a short time (it looks like 7 days when the new server opens). Many prizes can be obtained from the starter project.