I’ve just completed a nightfall with 108k points and with a lot of Calus-themed gear and I didn’t get the Triumph
I've done the High Roller Nightfall Triumph on my Warlock and you don't need to use Calus themed gear and weapons in every slot. As I had Lunafaction boots and the Swarm of the Raven on,but everything else was from the Managerie.
It has to be ALL Leviathan themed gear. You can mix and match from Menagerie and the first 3 Raids. Bad Juju also counts.
Nighthawk does not count as calus themed.