Loki was Nyssa's personal robot, who accompanied her on many of her missions, including her visit to Helheim.
He once corrupted his hard drive when he was scared by his own shadow, which Nyssa had erased to restore him. When he arrived on Helheim, Loki interacted with the base's computer EDGAR, which downloaded a copy of the computer into his memory.
Nyssa's former companion Tegan Jovanka contemptuously referred to him as R2-D2. (AUDIO: Cobwebs)