Many communities are started without a clear mission and values. Writing a manifesto is a great way to clarify the whys of a community.
Once a manifesto is written, share the link to collect signatures from the community. Activists are rewarded with burn tabs each time they sign the manifesto. If a manifesto is the kindle that lights the fire, then the burn tab is the fuel that keeps the fire going. Each time activists sign the manifesto or gift the tabs to each other, the burn timer is extended.
In short, the burn event is an initiation ritual to turn your mission into a community, and your community into a movement.