Dusk is actually a revenant, a returned one, someone who cheated death. When he uses too much of his ability, reality sort of cat6ches up and the script code upholding reality begins to remember that he should be dead, stripping him of his corporeal state and threatening to end his life. Added bonus, the angry and offended dead come for him as he becomes a beacon that disturbs them and leads them to him. So he has to really weigh the pros and cons when using his psionic talents.