Treasure Chest Opened After Watching an Ad

Watching an ad to open the Old Treasure Chest in the Elf Forest rewarded me with 500 Gems. It's a 5% drop rate, and I've been pulling 500 Gems for three days straight. Old Treasure Chest (Elf Forest) Item Probability 500 Coins 0.1% 3,000 Gems 1.5% 5 Gem Booster: 1 hour 1.6% 5 Gem Booster: 30 minutes 2.5% 1,000 Gems 3% 500 Gems 5% 10,000 EXP Up 18% 5,000 EXP Up 28% 3,000 EXP Up 40.3%