What do I need to fight an overlord champion?

[hallow thicket]

I was attempting to solo the Exodus Gardens lost sector but was hit in the face with a barrier champion so I spent the next hour doing the arbalast challenge to unlock that, only to go back and defeat the barrier champion and have a overlord champion pop up, which I now also cannot kill

[hot topaz]

you have certain weapons that can deal with champions. Some exotics have that built-in automatically (Le Monarque in your case for overload). And then there is always mods on your artifact that give certain weapon archetypes champion mods permanently

This "season" for exmaple its Trace riifles and Machienguns that have overload, while sniper and Sidearm for example have anti barrier