Sleepwalker had several notable weaknesses. The first was his bond to Rick—whenever Rick awoke or regained consciousness, Sleepwalker would automatically disappear from the human world and return to Rick's mind. At the same time, Sleepwalker's strength was related to his connection with the ground and the Earth—the higher he levitated, the greater his loss of strength, although he gained his full strength when actually standing on the ground itself. Similarly, Sleepwalker would weaken if he did not return to the mental plane or Rick's mind to rest and renew his supply of mental energy, which happened both when Rick was killed during the Infinity Gauntlet and when Rick seemed to be dead (actually a ruse by Sleepwalker to protect him from Cobweb's minions). Prolonged stay on Earth can lead to death. Finally, upon being exposed to a certain frequency of light, Sleepwalker initially experienced hallucinations and other pleasurable effects that distracted him from his frustration and anger at being hated and rejected by humans, despite his attempts to help them. He became addicted to the light, using it to escape his problems in a way similar to drug abuse or alcoholism. Sleepwalker's obsession with the light had tragic consequences, including the creation of Spectra and putting Rick into a coma. Horrified at what he had done, Sleepwalker managed to overcome his addiction and saved Rick's mind from the invasion of the Thought Police.