Flodo Span

Flodo Span is a gaseous member of the Green Lantern Corps. He has no corporeal body, and holds himself together with his ring. He was a friend of Hal Jordan's, and a member of the Green Lantern Corps of the Kylminade.

Sentient Sector 3600
When Sinestro allied himself with the Sentient Sector 3600 to defeat the Green Lantern Corps of Earth (Hal Jordan, Arisia, John Stewart, Katma Tui, Kilowog, Ch'p and Salaak), Hal called in the Green Lantern Corps of the Kylminade to help them defeat Sinestro. Ultimately, it was Flodo Span who defeated Sector 3600 by using his ring to expand himself over the entire sector. The effort nearly drove him insane until he used his ring to re-gather himself back to normal size, after reducing Sector 3600 to the size of a baseball. With Sector 3600 gone, Sinestro was quickly defeated and taken to Oa for trial and sentencing.

Power battery implosion
Flodo's most notable activity in the comics is when he assists Hal Jordan in traveling through the dimensional barrier to speak with the Guardians of the Universe, after the execution of Sinestro triggered the implosion of the Central Power Battery on Oa, and the subsequent absorption of the Green Lanterns' rings. Flodo and Hal made it through to the Guardians, but in the process, Flodo's ring was absorbed by the Central Battery and his gaseous form dissipated.

Blackest Night
Flodo is one of the many fallen Lanterns to be risen from his grave on Oa to become a Black Lantern. He is one of the many Black Lanterns beginning a stand against the living Green Lanterns on Oa.

Oath
Flodo has his own oath in the comics:

Once there was but darkness, full and forever&mdash; but then came the light of the Green Lantern&mdash; and then myself&mdash; to do it justice!"