Threllips were an aggressive species.
Threllips were large creatures with arms as thick as tree trunks. They had at least four different DNA streams, creating different types of Threllips; "C" and "D" Threllip DNA streams were bred for labour work, the other streams were for leader types. They could become drunk on Earth alcohol. (AUDIO: Living Legend)
The Threllips were an aggressive species, known for conquering planets. They were governed by the Threllip Empire. The Eighth Doctor considered them socially primitive and incapable of joy. They measured time in decalongs and kept wartsnogglers as pets. (AUDIO: Living Legend)
The Threllips were technologically advanced; enough that they had dealings with the Time Lords. They travelled using transdimensional portals, allowing them to travel vast distances. They used radium-powered blasters, with a hand-held blaster capable of destroying an entire forest. Threllips were grown in birthing tanks and they had scanners capable of detecting temporal machines. (AUDIO: Living Legend)
On 11 July 1982, Vengorr and Thon were sent to Ferrara, Italy to set up a transdimensional portal so that the Threllips could invade. The Eighth Doctor and Charley stopped them by pretending to be Time Lords, sent to catalogue the turning point in history for the Threllip Empire.
They claimed that Vengorr would become the leader of the new empire and Earth was to be the first planet he would conquer. The Doctor showed Vengorr around Ferrara, which was celebrating Italy's victory in the World Cup. The Doctor claimed that they were suffering a plague called "the World Cup Fever". When a drunken human came too close, Vengorr threw him away. The Doctor claimed that Vengorr was infected from this and had to drink wine to cure himself. Vengorr became so drunk that he was unable to function and had to return to his homeworld, ostensibly to cure the fever. While the Doctor was showing Ferrara to Vengorr, Thon stayed behind to set up the transdimensional portal. When Thon asked about his fate in history, Charley claimed he would be forgotten completely except as the name of Vengorr's pet wartsnoggler. When Vengorr returned, Thon was so angry that they started fighting. While they were fighting, the Doctor was able to reprogram the transdimensional portal, sending Vengorr and Thon to one of the moons of Mordelius Prime. (AUDIO: Living Legend)