The Banner Riot was the infamous incident that led to the events that occured on July 16th, 2010. This, along with the aforementioned incedent, are usually considered the first real cracks in Solstice, with Avis Cyrus' demotion, the "Ahem" thread, and the forums divide in two shortly after, being the final blows.
This argument was petty at first. One of the administrators at the time, Avis Cyrus (Now Xenia) made a suggestion in the forum skins thread to change all banners that said "Nightmare Forums" to "Solstice Forums". This idea was universally praised and accepted, however, one of the other administrators, Skyler, had other ideas. He believed that to maintain part of Solstices history, the Nightmare banners should stay up. Avis disagreed, along with VTP, Adam, harryheart, and other notable members, that they should be replaced, citing that there were no PLF banners (one of the three forums that merged to create Solstice) on the forums. Skyler lashed out at Avis, and got his brother (his "brother" being authentic or a clone account by Skyler is still debated to this day) and Rucario to attack Avis in said thread. Avis, although under attack, had no choice but to close the thread with a post calling out the three. Skyler later abused his adminship to re-open the thread, and continue posting. Avis stopped replying, and struggled to find Hollow Abyss (Dream Eater), who, ironically, was out and not able to access Solstice at all. This later carried into the Solstice IRC, with Skyler, Rucario, and Tendo all trolling Avis.
Influenced by Rucario, Skyler would make a descision that would forever change Solstice. See The July 15th Incident.