A Phantom Trollbooth forces clans that attack you to contribute 10,000 meat to your clan stash. Clans without 10,000 meat in their stash cannot attack another clan with a Phantom Trollbooth. It costs 50,000 meat to install.
In-game description: "If you build this, attacking clans will have to pay the Troll Toll of 10,000 Meat in order to attack you. This Meat will go into your Clan Coffer."
- Attacking a clan with less than 10 bags of goodies and a Phantom Trollbooth comes out as a loss for the attacker meat-wise.