Edit: changed out Impact Damage and Combo Duration mods for Gladiator Set components - this is what I actually use, since that can stack more chance alongside Blood Rush.

This is meant to serve as a Stat-Stick for [Atlas], specifically for scaling up the effectiveness of his Landslide.

The Sancti Magistar's a good choice for a starting weapon for this: it's a high-crit-rate weapon that does impact damage, and it has a fairly good Riven disposition. However, the real reason it's being used here is because its base traits mean it doesn't even really need a Riven mod to be effective as one.

As such the build's made to use a low number of forma (just one Madurai, which is applicable for any other [Sancti Magistar] builds you want to use that don't use the other polarities.) If you do want to lean harder into this build, without attempting to collect/unlock/trade rivens, Replace the 60/60 elemental mods with their pure damage variants: North Wind and (Primed) Fever Strike. The 60/60 mods are used here since they're more economical for the damage output versus drain. To fit these mods, this will require 2 extra Forma with polarities of Naramon and Vazarin.

Because the purpose of this build is to serve as a starting-out stat stick, however, it could be preferable to look for different weapon/mod combinations, especially if the Rivens you have aren't for this weapon.