Betrushia was a planet in the Massatoris system, rich in minerals and jungles.
Millions of years ago, an advanced civilization on Betrushia created an organic catalyzer. It was meant to test species for survival traits, but it worked too well and consumed any living thing it encountered. Before being wiped out, the inhabitants built an artifical ring system to confine the catalyzer to Betrushia.
By 2148, the new inhabitants of Betrushia, the Cutch and the Ismetch, were at war with each other. The Seventh Doctor and Benny became involved in the war, but it became moot when the Chapter of Saint Anthony targeted the planet, inadvertently freeing the catalyzer. In the end, Betrushia was destroyed. (NA: St Anthony's Fire)