Trials of Osiris is a beloved tournament for Destiny series' PvP aficionados but it appears the lore attached to it may have shined some light on the storyline that will be present in the next Season. Evidently, there will be spoilers ahead.
Destiny 2's lore fans tend to dig up a lot of good stuff that is usually hidden below the little lore we get in regular campaign missions. It happened again with the lore behind Trials of Osiris when BC1096 posted a massive find about Trials of Osiris on Reddit. The "massive" part refers to both what this means for Destiny 2's storyline and the actual size of the post so here is a quick rundown.
Trials were initially kicked off by Brother Vance, Osiris' follower, after he figured out that the spire that we know as the Lighthouse would play a sound when a Guardian dies. Upon many other Guardians' temporary deaths and one permanent, the spire played enough sounds for Vance to decrypt that the Guardians have a dangerous potential in them.
He goes on to share the discovery with Mara Sov but is surprised to see that she is already privy to this information. She warns Vance against pursuing things he apparently can't comprehend further but he then goes to Osiris, who also pretty much repeats what Mara said but also chastises the follower, leaving him heartbroken.
Among this back and forth, Mara told Vance to bring a message to Osiris which is not revealed until the latter two converse, where Vance tells him to "plant the seed". Osiris had picked up a seed that came from the Darkness during his travels, which could be the thing that is referred to in this convo.
Osiris finally sends Saint's Vocation ship to Saint-14 which brings a message to the latter, boiling down to stating that Lighthouses are not what they seem and "may bring ruin we have no answer for".
Essentially, what Vance found out and what Osiris and Mara Sov already knew is that Darkness is approaching and Lighthouses will play a part in bringing it closer. While Vance initially thought he was the only one who could hear the Lighthouse's music, it turned out others could too.
Now the fans are speculating that Vance has an affinity for the Darkness which is approaching for another duel with the Traveller and that will be the setting of Season 11 in Destiny 2.