The Carbide Challenges are tied to the Carbide outfit you get at Tier 1 of the season 4 battle pass.
|Reach Season Level 10||Carbide Chest Plate|
|Reach Season Level 20||Carbide Leg Armor|
|Reach Season Level 30||Carbide Bracers|
|Reach Season Level 40||Carbide Mask|
|Reach Season Level 65||Carbide Chest Armor|
- Complete any 3 Carbide challenges to earn the reward item, the Positron Harvesting Tool.
- Basically this means you will get the Positron Harvesting Tool when you reach season level 30.