The third city relics are dropping since today, 25 September. They drop from level 7-10 goblin camps.
Tips for farming relics
Aim for higher level goblin camps as they have a higher percentage chance of dropping relics.
I’d personally recommend level 9-10 camps but level 7-10 are also dropping.
For level 9-10 goblin camps, send Tier 3 or Tier 4 troops. Around 40k-50k-60-70k, as many as you have. After 60k-70k, complete your army with Tier 1. The enemies will kill your Tier 1 troops first so you don’t need to worry about losing Tier 3. You will obviously perform better as your army has Tier 3 troops.
Send your highest level heroes as this also increases your chance of getting relics.
Last but not least, “Sage Tower”. If you plan on hunting 100 city 3 relics, upgrade your Sage Tower to level 10 if possible. If you don’t have the “hobbit building crew” item, make sure to have your Sage Tower upgraded to level 9.
Use attack and defense runes if you have any.