In Lords of the Fallen, before you can upgrade your weapons, you must first locate the blacksmith named Gerlinde, who is integral to the weapon enhancement process. Additionally, you need to gather various upgrade materials scattered throughout the game, such as Rune Shards and Magic Runes. These materials determine the type and level of upgrade you can apply, making them essential for enhancing your weapon's capabilities.
LOTF: How to Upgrade Weapons
To upgrade weapons in Lord of the Fallen, you need to rescue Gerlinde the Blacksmith. Start by going to Vestige of Blind Agatha, defeat the enemies and get the Prison Cell Key to free Gerlinde. When you complete this, go back to Skyrest and Gerlinde will allow you to upgrade your weapons using Vigor and Deralium items.
After you defeat Pieta, you will eventually cross cliffs to reach Pilgrim's Perch Bellroom. Use a lift to descend to the Vestige of Blind Agatha, kill the nearby enemies, and drop onto a metal cage that holds Gerlinde and other prisoners captive.
To release them, you'll need to defeat a knight with mace and shield and get the Prison Cell key. Once you get the key, talk to Gerlinde and choose "Hand over Prison Cell Key" to unlock the prison cells and free prisoners including Gerlinde the blacksmith.
Go back to Vestige of Blind Agatha resting area, choose warp to Vestige, and fast travel back to Skyrest. Talk to Gerlinde in Skyrest and choose "Upgrade Equipment", and you can upgrade your weapons in exchange for Vigor and Deralium fragments.
By upgrading your weapons, you can add damage and gain rune slot. For example, to upgrade from Crimson Rector Sword to Crimson Rector Sword+1, it costs 500 Vigor and 2 small Deralium fragments. By upgrading this sword, you will boost attack power from 135 to 155, physical damage from 130+4 to 149+5, and gain 1 rune.

Weapon upgrades are determined by the size of the Deralium fragments:
Item | Upgrade |
---|---|
Small Deralium Fragment | Up to +3 |
Regular Deralium Nuggets | Up to +5 |
Large Deralium Shards | Up to +9 |
Deralium Chunk | Up to +10 |
Deralium items can be obtained by completing quests, defeating enemies, or finding them in chests. In Revelation Depths, you can find it near stone structures after clearing out miners. In the Tower of Penance, it's inside a chest located in a jail cell after navigating through wooden platforms and defeating the Ardent Penitent. At Bramis Castle, it's obtained by navigating through the King's bedroom balcony and descending a crystal. In the Fief of the Chill Curse, after defeating The Hollow Crow, players can find the chunk in a chest next to a beacon.