Summoners War - Rune - Grade

There's 6 different Rune Grade! Each Rune, when created, will receive a Grade. Represented as a Star (like Monster). Each Grade give randomly a intensity for Stat and Sub-Stat! Higher is the Grade the more the intensity of each Stat and Sub-Stat will be high and of course the value of the Rune will raise! Each Rune Grade are given as a Reward in Scenario, but the Difficulty of the Scenario we choose will raise the Grade, in Giant's Keep, Dragon's Lair and Necropolis the higher is the Base the higher Rune Grade chance is present and in World Boss the higher is the Treasure Box higher Rune Grade chance is present!

Grade	Obtain
1*	Battle Map - Scenario - Normal
2*	Battle Map - Scenario - Normal Battle Map - Scenario - Hard<
3*	Battle Map - Scenario - Normal (Stage 7) Battle Map - Scenario - Hard Giant's Keep, Dragon's Lair & Necropolis
4*	Battle Map - Scenario - Hard (Stage 7) Battle Map - Scenario - Hell Giant's Keep, Dragon's Lair & Necropolis
5*	Battle Map - Scenario - Hell (Stage 7) Giant's Keep, Dragon's Lair & Necropolis
6*	Giant's Keep, Dragon's Lair & Necropolis

For Giant's Keep, Dragon's Lair & Necropolis, I'm not sure what they can give in Low Base, but in High Base like B8 to B10 we can find 4 to 6* Runes!