T2 celestial alloy where ??

Asher1_1

Not in BG store
Not in Glory store
Not in Radiance store

My t3 cosmic alloy is expiring

TotemCorruption

We don't have that resource yet.

You can use T3 class alloy to take a 6* relic from rank 3 to rank 4. It requires T3 class alloy, T4 basic alloy, and T1 celestial alloy, all of which are available.