To upgrade your Poison Forge ruin, you need Poison Forge Shards.
With each upgrade, you need more Poison Forge Shards.
Below is a list of possible ways to gain these.
Gems
You can purchase Poison Forge Shards using gems.
1 Poison Forge Shard = 15 Gems
10 Poison Forge Shards = 125 Gems
100 Poison Forge Shards = 1,154 Gems
1000 Poison Forge Shards = 10,000 Gems
Chest
You can purchase a chest using guild coins to have a chance at
gaining extra Poison Forge Shards.
To purchase, click bag, click chests, click the third icon on right hand side.
The chest is called Magical Shard Box and costs 22,500 Guild Coins.
It randomly gives you 10 shards for any of the ruins or statues.
Campaign Elite Sweeps
You can sweet elite campaigns to pick up extra Poison Forge shards.
Elite 8-1
Elite 8-2
Elite 8-3
Elite 8-4
Elite 8-5
Elite 8-6
Chests
Chest from the VIP daily clan gifts (Nightspear city) gives Poison Forge shards too.
VIP Daily Clan Gifts
You can collect 3 Poison Forge shards per gift from daily VIP Clan gifts (Once you have level 25 diplomacy for this city).