New system introduced in the half anniversary for all servers and a pretty good one to get stats for everyone in your account.
With the half anniversary update they introduced a new type of dungeon; Elemental Dungeon.
Each day of the week will feature a different element you can farm and/or sweep up to three times.
Only the big glowing nodes apply to everyone in the account if it’s passive stats (usually % instead of flat ones).
The small nodes only apply to the character you are training.
You can check the total stats in your buff bar, under your profile.
Considering you have to use souls, skill pages and the new currency, I would only invest in meta units: Tiamat, NEO Bedivere, Lancelot, etc.
Units you know will last for a few months and not waste Elemental Stone
Elemental Stone Description Stones obtained from the Element Dungeon. Used in training to enhance a specific element. Sources Element Dungeon , since you cannot reset the training tree and get your materials back.