Reapers and rifts
Clear Temple rooms for Reaper drops
Pursue random Reaper drops while advancing through Slorm Temple rooms you can clear consistently.
Slorm Temple, while progressing through and clearing rooms.
Repeatable through further Temple progress. Reaper drops are random, and this route does not guarantee a particular weapon.
Stop when you have the Reapers you need or switch to closing Rifts if that activity better suits your current progression.
Open a guide to find other locations and see what the item is used for.
Pursue random Reaper drops while advancing through Slorm Temple rooms you can clear consistently.