Lerna was the first daughter of Typhon and Echidna, and embodiement of healing, regeneration and parasitism. She was a snake-like being, made of an organic, gelatinous substance. She could shape-shift her body to suit the current occasion, creating long tentacle-heads to attack, and her mutant body could heal from nearly any wounds, with the exception of fire-based ones. Her main attacks consisted of creating a number of heads(usually 9) and claws and attack the enemies with bites and slashes. She could control the wounds she inflicted, preventing them from healing or heal in incorrect ways. Also, if she could bite and hold the enemy with at least 4 mouths, she could command to the body's cells to grow at an alarming rate, thus forming tumors.
But Lerna's most lethal attack was the ability to envelop other living beings, bond with them and control their body, mind and powers. During the war with the Gods, she was a real pain in the ass to bring down, but in the end she, with the other Titans, was banished in the Tartarus.
There, Lerna tried to fuse herself with Leviathan, to get power and possibly take her father's place. However Leviathan fought back, and forced her out of his body. He took her and tortured her for three days, before hurling her away, towards Fenrir's iceworld, knowing that cold would prevent her from regenerate her wounds. Mortally wounded and a step away from death, Lerna called for help, to anyone. From the cold, freezing wind, someone answered and took her in his claws, bringing her away. She found herself standing in front of Loki's ice throne. The god had observed her carefully, and had already some plans for her. For Lerna the god's palace wasn't a better place than Fenrir's reign, for even the Emperor lived in an ice kingdom. He offered her a deal: being his queen, for all eternity, in exchange of living on and having the power she always wanted. She accepted, and fused with him. This fusion gave Loki, who's the one in complete control, the power to heal from anything, and powered up his shape-shifting abilities with Lerna's own one. From that day, they live toghrther in the Great Deceiver's palace, plotting and creating demons, altogether with their offspring.