In the darkness of the underworld, the Bakemono signal alarms and warnings over long distances using great horns. These are usually only used far below ground where no human would hear. Tu-Ning has brought one of the great instruments to the surface, and for the first time, people have listened to the off-key and mournful note... though none have yet lived to tell of it. The Bakemono know to go to the horn when it is blown, encouraging more to appear from the shadows and those fleeing to return to the horn as a place of safety in numbers, a rallying point if you will.
Adding Tu-Ning to your force gives the Rally Ki Feat, which is easy to use with the Ki-rich Bakemono Horde Cards, also, the ability to summon an additonal model per turn infuriates opponents!