Greenwood Ancients is an epic elder that gains strength for each stronger enemy unit when it is damaged. Its strength and ability can be increased by leveling it up. Greenwood Ancients is a durable unit that requires special conditions in order to regain its strength.
Greenwood Ancients can be interestingly hard to remove as it will gain strength depending on how much damage it takes.
Like when playing against Scrapped Planners and Earthfathers, you can try to destroy Greenwood Ancients with one card so it doesn't trigger its ability.
Greenwood Ancients can be used to exploit large, strong hordes of enemy units, similarly to Sharpfist Exiles.
When planning out how to play Greenwood Ancients for the most value, remember that it will only gain strength according to the number of stronger enemies compared to its damaged strength, not its original strength.