Which device is specifically designed to elevate stage lighting?

The device specifically designed to elevate stage lighting is the light tree. A light tree is essentially a vertical support structure that allows multiple lighting fixtures to be mounted at various heights. This arrangement creates better distribution of light across the stage, enhances visibility, and can be adjusted to suit specific performance requirements.

Other devices mentioned serve different purposes in a digital event context. For instance, a sound mixer is essential for managing audio levels and effects during an event, while a seamless switcher is used for switching between different video sources without interruption, enhancing the visual experience. A riser, on the other hand, is typically used to elevate performers or equipment but is not dedicated solely to lighting. Hence, the light tree stands out as the correct choice for the specific task of elevating stage lighting.