Destiny 2's Blasphemer is a kinetic slug shotgun that was released in 2019 with Shadowkeep. It was sunset in Beyond Light but was reprised in the recently released Season of the Chosen. Blasphemer isn't a gun players can get with ease, and there are specific rolls to be on the hunt for.
Destiny 2 Blasphemer: How to Get and What Rolls to Look For
Blasphemer can only be obtained two ways, both involving activities on the Moon. The first, and more accessible way is through the Altars of Sorrow.
The Altars of Sorrow is a wave based activity where players team up to fight hordes of Hive. At the last wave, players will fight a powerful "Nightmare" enemy, and defeating them rewards players with a weapon. There are three possible weapons to get from Altars of Sorrow, each on a daily rotation, and the Blasphemer shotgun is one of them. Before you attempt to farm it, make sure Blasphemer is the gun on rotation that day.
The second way to get Blasphemer is through the dungeon Pit of Heresy. However, this way is a lot more difficult, and will likely require a fireteam to complete. Plus, unlike Altars of Sorrow, there's no guarantee to come out with Blasphemer if the dungeon is completed, as there are other guns in its loot pool.
What Rolls to Look For
Blasphemer is a powerful weapon in PVP. It resembles the exotic shotgun Chaperone, both being kinetic slug shotguns. For PVP, the rolls to look for here is Quickdraw for the first perk, and Opening Shot for the second. Hammer Forged Rifling and Accurized Rounds are good barrels and magazines to have too. This perk combination is actually the curated roll of the gun, so the PVP god roll for this weapon is its curated form. Other strong perk alternatives for PVP include Snapshot Sights and Swashbuckler.
For PVE, the gun is less powerful but still decent. Look for the Fourth Time's the Charm for the first perk, and swashbuckler for the second. Fluted Barrell and Assault Mag are the best barrel and magazine to have. Some decent alternatives include Rampage and Surplus.