In semiconductor devices, hydrogen has traditionally been viewed as a panacea for defects, being adept at neutralizing dangling bonds and consequently purging the related states from the band gap. With amorphous silicon nitride (a-Si3N4)─a material critical for electronic, optical, and mechanical applications─this belief holds true as hydrogen passivates both silicon and nitrogen dangling bonds. However, there is more to the story. Our density functional theory calculations unveil hydrogen's multifaceted role upon incorporation in a-Si3N4. On the "Jekyll" side, hydrogen atoms are indeed restorative, healing coordination defects in a-Si3N4. However, "Hyde" emerges as hydrogen induces Si-N bond breaking, particularly in strained regions of the amorphous network. Beyond these dual roles, our study reveals an intricate balance between hydrogen defect centers and intrinsic charge traps that already exist in pristine a-Si3N4: the excess charges provided by the H atoms result in charging of the a-Si3N4 dielectric layer.