When Affixing, it is possible to increase the number of slots on the base item by one by using the Extra Slot. When using the Extra Slot, the success rate of all Augments will be lowered by a certain percentage depending on the number of slots. An item can have a maximum of 8 Augments. Lower rarity weapons will have more augment slots, exactly how it used to be in base game. I think Stygian Zinogre patch will add an extra slot to all weapons, but that's it.

1. How To Increase Augment Slots Mhw Weapons
2. How To Increase Augment Slots Mhw Slot

You can use these slots by using the Streamstone and a gem which originates from a powerful monster. The Augmentations can increase anything from attack to affinity to defense and health regeneration. Select the equipment you want to upgrade in the screen. Grey items represent equipment that you cannot upgrade, as you do not have the materials but you can easily upgrade the white items.

Fully upgraded weapons and armors can be augmented to further enhance their power. Augmentations require rare monster materials and Streamstones. Streamstones can be obtained by completing Tempered Investigation.

Tempered Investigation

Tempered Investigation quests are randomly awarded when the player gathered tracks from tempered monsters.

The following monsters do not have Tempered variation: Great Jagras, Kulu-Ya-ku, Tzitzi-Ya-Ku, Great Girros, Dodogama, Zorah Magdaros, Xeno'jiiva

Tempered Investigation Reward

Completing tempered investigations reward the player with various streamstones and feystones. Streamstones are used for augmentations, feystones can be appraised and yield decorations.

Streamstone

Streamstone shard, streamstone, and gleaming streamstone are used as:

• Key ingredient for Melding Pot
• Primary ingredient for Armor Augmentation
• Secondary ingredient for Weapon Augmentation

Sullied Streamstone and Shining Streamstone will be appraised and identified as Warrior's streamstone and Hero's streamstone. Warrior's streamstone and Hero's streamstone are the primary ingredient for weapon augmentation.

Weapon Augmentation

Fully upgraded weapons can be augmented to further enhance their capability. The following augmentations can be added to weapons:

Weapon augmentations can be overwrite; however, materials used for previous augmentation will not be returned. Weapons of different rarity requires different materials to add augmentations:

How To Increase Augment Slots Mhw Weapons

How To Increase Augment Slots Mhw Slot

Armor Augmentation

Armor augmentation has one single option: Upgrade Limit Removal. This augmentation increase the maximum upgrade limit for the armor; allowing the armor to increase its defense.