Plutonium is an add-on module for FoundryVTT, available for free to the public.
Plutonium’s main feature is its full compatibility with the 5eTools dataset, allowing dungeon masters (and players!) to easily and automatically import content they already own with just a few clicks.
It also adds various quality-of-life (QoL) features, such as UI enhancements, mass-update tools, and a character-builder (currently beta; available for Patrons).