When the forest comes for you, it goes hard. They're on their warpath and they're not going to stop for anything. Check out the upcoming Path to Glory rules for the Sylvaneth which will be in their new battletome for Age of Sigmar.
From the article:
Every new battletome for Warhammer Age of Sigmar contains Path to Glory rules for expanding your army as you wage war on your enemies – and with Battletome: Sylvaneth, you can grow from a single acorn into a huge forest to thwart your foes. No, seriously, the rules for the Sylvaneth are all centred on growing your Wyldwood stronghold into an increasingly formidable forest!