M is for... Mara

A malignant entity which manifested itself as a giant serpent. The Mara was created by accident on the planet Manussa, when its people experimented with mind expanding techniques to boost their mental powers. A perfect blue crystal was manufactured, which allowed them to focus their minds.

The shared minds of the users of this crystal led to an unexpected outcome - the amalgamation of the dark side of their minds resulted in the creation of the Mara.

The planet became part of a federation of worlds, and its first Federator succeeded in destroying the creature. However, it was only banished to the "dark places of the inside" - the deepest levels of the subconscious. It was maintained by feeding on fear, but constantly sought ways to remanifest fully.

The Doctor and his companion Tegan first encountered the Mara on the idyllic world of Deva Loka. It was home to a seemingly primitive tribe called the Kinda, but the Doctor deduced that they had once been a technologically advanced people. The Kinda knew of the Mara and their legends told of how its coming triggered disaster in a never-ending cycle. To protect themselves from its manifestation, the tribe refused to dream alone. Only in group dreams could the strength be found to keep the Mara subdued.

However, Tegan fell asleep in a forest glade and left herself open to possession by it.

She found herself in a black void, populated by bizarre ashen-faced individuals. One figure in particular - a young man named Dukkha - tormented her into willingly accepting possession by the Mara. She awoke with a snake-like tattoo on her arm, and she was now cruel and devious.

She quickly passed on the Mara to a young Kinda tribesman named Aris, as through him it could dominate the entire tribe.

The Doctor realised that evil could never face itself, and so had Aris surrounded by reflective panels from the base of an Earth expedition. The tattoo became a real snake, which fell to the ground and rapidly grew into a gigantic serpent. Trapped in the circle of mirrors, it exhausted itself and retreated back to whence it had come. The Doctor tried to reassure Tegan that she was now free of its malign influence.

However, it was only lying dormant. When Tegan rejoined the TARDIS crew after a period back on Earth, the Mara took advantage of this by making her unconsciously alter the ship's co-ordinates to take it to Manussa. They arrived just before a ceremony was due to take place which celebrated the Federator's defeat of the Mara. The Great Crystal which had created the Mara was held in the city museum, whilst a dummy one was used in the ceremony. A mystical group known as "Snakedancers" constantly warned the authorities against the potential return of the Mara, but they had gradually become ignored as eccentrics, and the Mara itself had lapsed into legend.

The possessed Tegan was used to manipulate the museum director and Lon, son of the current Federator, to ensure that the real Great Crystal was used in the ceremony - allowing the Mara to manifest itself fully once more.

The Doctor made contact with Dojjen - last of the Snakedancers - who showed him how he could counteract the Mara using a smaller offcut from the Great Crystal.

When a giant snake materialised at the ceremony, feeding on the fear it generated among the Manussan crowds, the Doctor focused his thoughts through the smaller crystal to destroy it.

This time Tegan really was freed of its influence.

Played by: Janet Fielding (Tegan), Jeff Stewart (Dukkha), Adrian Mills (Aris), Martin Clunes (Lon). Appearances: Kinda (1982), Snakedance (1983).

• The Mara was created by writer Christopher Bailey, an academic from Brighton. Rumours abounded that this was an alias for another author - ranging from playwright Tom Stoppard to pop star Kate Bush.
• Kinda in particular is full of religious references. Deva Loka represents the Garden of Eden, and the Mara is the serpent which tempts Eve - at one point the possessed Tegan hides in a tree with an apple. 'Dukkha', however, derives from Buddhism - it means suffering / unhappiness.
• In the Torchwood episode Small Worlds, Captain Jack speculates that the ancient Faerie creatures he encounters in Cardiff may be part Mara, suggesting that it can also influence the elements.
• The snake prop in Snakedance was a massive improvement on the big pink plastic one seen at the conclusion of Kinda (which now has the option to be replaced with a CGI version on its DVD / Blu-ray). However, for its death scene, the pump spewing out the pink and green gunge malfunctioned, causing it to make loud farting noises - an outtake which can be seen on its DVD.