These Awakening Stones are used exclusively for Awakening 5★units, and you need at least four duplicates/Awakening Stones to fully Awaken them.
What Are Awakening Stones For?
Guidestones can be used when Awakening 3★ and 4★ units, but not 5★ units. Only Awakening Stones can be used if you want to increase their Awakening Stage. Currently there are three available Awakening Stages (as of this writing, Awakening Stage 4 has yet to be unlocked by the devs). Here are the bonuses you get per Stage:
How To Get Awakening Stones
There are only two ways that you can get Awakening Stones in the game:
Method #1: Pulling Dupes
Awakening Stones are dropped whenever you pull a duplicate of the 5★ unit you already have. Hence, you’ll have to rely on RNG to get those Awakening Stones by pulling a lot from the Guide system. It’s a long shot, but remember that you can beat the game with minimal Awakening levels for your 5★ units. TIP: If you want the highest chances to pull a duplicate, remember to only pull on the rate-up banner of the unit you want to fully Awaken. That’s why if you want to max out a specific character’s Awakening Stage, I recommend saving up for their banners instead of pulling often on random banners.
Method #2: Buying Sacred Seals From The Exchange Shop
If you don’t want to rely on RNG, then you’ll have to hit pity on the banner of the unit you want to Awaken them at least once. By doing so, you’ll be able to buy their Sacred Seal with the Guide Fragments you’ve accumulated from pulling in the Guide Fragment Exchange Shop. This unit-specific Sacred Seal allows you to summon that specific 5★ unit only — with no pesky 50/50 rates or the chance to get lower rarity units. TIP: You need 200 Guide Fragments to buy a unit’s Sacred Seal in the Exchange Shop, which means you need to pull on a specific banner 200 times. In short, you’ll have to spend 6,000 Rubies on a regular, non-step-up banner to hit pity! That is a lot to save up for — especially if you’re F2P, so be prepared.