Abstract: A vapor chamber device having a first vapor core configured to passively spread heat from a localized first input area to a relatively larger first output area adjacent to and in thermal contact with a heat output side of the vapor chamber device, and a second vapor core configured to passively spread heat from a localized second input area adjacent to and in thermal contact with a heat input side of the vapor chamber device to a relatively larger second output area in thermal contact with the first input area of the first vapor core. The second vapor core is configured to attenuate high heat flux hotspots on the first input area before the heat fluxes thereof pass through the second output area of the second vapor core to the first input area of the first vapor core.