These chests are only available during the 9th Anniversary Hero Wars Dominion Era Event.

What is in the Secret Treasure Chests?!
This was the reward for the 9th Anniversary Easter Egg Task for Day 1 (but not for Day 2?). Thanks to my comments for sharing what they received!

25 Red Artifact Essences
25Red Artifact Scrolls
25 Red Artifact Metals
500 Skin Stones (Agility, Strength, OR Intelligence!)
What's in the 9th Birthday Box?

Thanks to my comments for sharing what they received!
Red Artifact Essences
Red Artifact Scrolls
Red Artifact Metals
Skin Stones (Agility, Strength, OR Intelligence!)
Chaos Particles
Chaos Cores
Blue Runes