Killballs are large, spherical, Forge objects that can be placed on Sandbox in Halo 3, Forge World in Halo: Reach, and every map of Halo 4. Once spawned, they become static objects that kill everything on contact. This isn't true however for the Halo: Reach Killball; when put in front of a man cannon it will fly away. This is only if it is put on "normal" while it is spawned in mid-air.