Which weapons, quests, and items are leaving Destiny 2 when Season of the Dawn ends?

Since the release of Shadowkeep, Bungie has decided to take a new direction when it comes to Seasons in Destiny 2.

In an attempt to foster player retention and create what Bungie calls ‘had to be there moments’, a large slice of the content and ways to obtain items that was introduced with Season of Dawn will leave once Season of the Worthy begins on March 10th.

Here is a list of the items and activities that will be leaving:

• Season of Dawn Season Pass and bonuses from the Season Pass (previously earned items from the Season Pass can be claimed here) -- These bonuses include XP Boosts and Currency Boosts.
• Season of Dawn Seal and Savior title -- The Title/Seal itself will not be leaving the game, if you have earnt the Title then you will still be able to display it. Only the ability to complete the associated Triumphs will be leaving as these Triumphs are being retired. If the associated Triumphs have been completed the player will still be able to claim their Title.
• Incomplete items in the Season of Dawn collections badge will turn invisible
• Emblems and Shader Quests/items from the Season of Dawn
• Lore - "Constellations" 
• The Lantern of Osiris seasonal artifact

• Player power increase from The Lantern of Osiris -- This is an important one as many players will notice their Power level dropping by a significant amount depending on what their play time was like during the Season. For some players this could be a sudden 30-40 level decrease so be sure to be careful when doing high level activities early next Season as they will be harder than you remember.
• Polarized Fractaline
• Obelisk Bounties
• Timelost Weapon Bounties
  • The weapons themselves will not be leaving the game, only the ability to obtain them. Be sure to farm those god rolls in the last week while the ability to donate to the Empyrean Foundation is still active as donating gives a flat 25% progression towards all the Timelost bounties in the player’s inventory.

• Timelost Friends consumable
• The Sundial Arena -- Yes the entire Sundial activity will be leaving once Season of the Worthy starts. This is quite disappointing as the Sundial was a fairly decent activity with a quick run and a very good reward system once the Planetary Obelisks were upgraded as it gave out 4 weapons for each completion of the activity.
• Fractaline Skimmer consumable
• Light-Fused Fractaline 

• The Sundial Spire
• Destination Obelisks -- Make sure to fully upgrade these Obelisks and grab all the unique Seasonal mods that can be unlocked through these Obelisks. Bungie announced a recent change that starting in Season of the Worthy, Seasonal Armor will not only be able to take the current Seasonal Mods but also the previous Season’s Mods and the following Season’s Mods. Season of Dawn Mods can be fairly powerful if the player’s loadout is built around them so be sure to grab them for next Season.
• Tower Obelisk
• Quests from Osiris
• Quests from Saint-14 (The Bastion Quest will still be available)
• Saint-14 bounties
• Devil's Ruin exotic quest (Devil's Ruin will be available again in a future season) -- It was said by Bungie some time ago that Exotics tied to Seasons like Devil’s Ruin and Leviathan’s Breath would return sometime in the future but have yet to say how long into the future that will be and under what circumstances they will return. Best to complete the Devil’s Ruin quest now before Season of the Worthy starts.
• Season of Dawn artifact mods

So, all in all, be sure to obtain or complete as much of the above as you can before March 10th as once that day hits, everything listed will be gone from the game.

It’s entirely possible though that Bungie will decide to bring back certain activities or weapons depending on player feedback, as is the case with the recently announced Trials of Osiris. Best to err on the side of caution though.