Adventure Hook by Albert Parareda Sala
Because of the intense activity of the volcano Kaza in prehistory, Farzeen subsoil is rich in minerals and other valuable materials. To help their fight on the island a small group of Tcho-Tcho, with help from the Fungi from Yuggoth, is extracting those materials. Can the heroes defeat the well-equipped Tcho-Tcho force? Will they discover the secret of their riches? Neither the Mi-Go nor the Tcho-Tcho will tolerate any intrusion in their mines…