Berserker shields are a reward for the Fist of Guthixminigame. Berserker shields, like many other Fist of Guthix rewards, degrade in a similar fashion to Barrows equipment. They come in 2 metals: adamantite and runite, with the former requiring 45 Defence to equip while the latter requires a level of 55.
Berserker shields are repaired by paying Reggie a small amount of fist of guthix tokens. They may also be immediately and completely uncharged by Reggie free of charge; this must be done in order to sell the shields, as they are untradeable in their charged state.
If the player does not wish to earn the full 100 (adamant) or 300 (rune) tokens to purchase the shield at the Fist of Guthix minigame, they may purchase the uncharged shield via the Grand Exchange and recharge it for 10 or 30 tokens respectively.