Hairy Chestnuts is an epic toad elder that drains strength from the enemy base when it takes damage. Its strength and ability can be increased by leveling it up. Hairy Chestnuts fits well into decks as a win condition due to its ability to damage the enemy base.
Hairy Chestnuts can serve as a valuable source of base damage for a deck.
You can trigger Hairy Chestnuts' ability yourself with cards like Toxic Sacrifice or Conflicted Drakes. Poisoning it can be especially effective as it will trigger every turn.
Note that Hairy Chestnuts will not damage the enemy base for its maximum amount if it takes a small amount of damage. For example, poison damage will only cause Hairy Chestnuts to drain 1 strength.
Like most elders, try to play Hairy Chestnuts in front of multiple enemy units so it can trigger its ability multiple times.