Reforge Stones become available at max level, and allow you to change the attribute of your gear.
Once you acquire a Reforge Stone, head to the Blacksmith and press the Reforge tab.
You will get this UI to select the attribute you wish to change, and the option to select a Stone to randomly obtain an attribute of that stone family. You can unlock up to 3 attributes per gear at Rank 11 and Rank 16. When the item has three attributes from that family, the stone family set attribute unlocks.
In Diablo Immortal technical alpha, Paragon is unlocked at level 45. It will unlock at level 60 when the game is launched. There are four types of Paragon, and so far it looks like a linear progression:
I have played through most of the Diablo Immortal technical alpha questline up to level 41 if you want to read through the story, and see all the vendor UI and systems in place.
The Diablo Immortal in-game shop offers only three items at the moment: Legendary Crest, Reforge Stone, and Platinum.
These can only be purchased with Eternal Orbs currency — which is obtained with Real Money.
Legendary Crest: Each Legendary Crest adds two random modifiers to an Elder Rift, grants Fading Embers to all party members, and guarantees you a Legendary Gem drop and 3 Runes.
With access to the Diablo Immortal Technical Alpha, I was able to explore most of the systems you are interested to know about. Here is a sneak preview of some of them.
Blizzard Entertainment has broken the long silence to dump tons of new info about Diablo Immortal Technical Alpha, providing details about the story and gameplay, screenshots, artwork, videos and more.