Gisela

Gisela was an Angel from Innistrad. She was the leader of the Flight of Goldnight. She was eldrazified by Emrakul and slain by her own sister.

The Four Sisters
Gisela, Bruna, Sigarda and Liesa are described as sisters and are older than Avacyn.

The Flight of Goldnight
Gisela and the Flight of Goldnight are associated with the sun, in contrast with Avacyn herself. Once a year during the Harvest Moon season, the sun will not dip below the horizon for two full days, and during this time the moon isn't visible. Known as the Feast of Goldnight, this is the holiest day for the humans. It is the time when the Avacynian enchantments are strongest throughout Innistrad. Angels from this flight are the most battle oriented among the flights. They also oversee the training of cathars.

Loyalty to Avacyn
Of all the angels, Gisela is closest to Avacyn, being her confidante, and fell into the greatest despair over her disappearance.

Corruption
Perhaps due to this closeness, Gisela fell completely in with Avacyn's will after she was corrupted, siding with her on the desire to wipe out humanity. She, Avacyn and Bruna showed up at Sigarda's house, trying to intimidate her into joining their crusade.

After Avacyn's death, Nahiri managed to summon Emrakul into Innistrad. This resulted in Bruna and Gisela being mutated into a horrific amalgamation Brisela that enforced Emrakul's will. Brisela was killed by Sigarda.