Primary Merciless arcane

[Toxic masculinity]

is this a new arcane? and it goes for weapons only? i mean main weapon or guns?
and can i buy it from other players or i need to do the steel path?

[Goosetave]

It's a new arcane for primary weapons (there is a version for secondaries). You can buy it from players but i don't recommend, it's very expensive for how easy it is to farm. You get one guarenteed arcane drop on acolyte kills in steel path, and there's 6 sets total, all of them useful. With a good team, steel path survival is a good way to farm it. Also you should be aware that a weapon needs an arcane adapter to equip an arcane, which you can buy from teshin for a bit of steel essence (you'll get more than enough while farming acolytes).