Arcane spirit shield

The arcane spirit shield requires 75 Defence, 70 Prayer and 65 Magic to wield. The shield is made by attaching an Arcane sigil, a rare drop from the Corporeal Beast, to a blessed spirit shield. This process requires 90 Prayer and 85 Smithing. Players without the required skill levels to create the shield may ask Abbot Langley in the Edgeville Monastery to combine the sigil and the blessed spirit shield, for a fee of 1,500,000 coins.

This shield's defensive bonuses are identical to the blessed spirit shield, but it provides a magic attack bonus of +20. The arcane spirit shield's counterpart, the spectral spirit shield, instead provides a magic defence bonus of +30.

Comparison
The shield has the same defensive bonuses as the blessed spirit shield, though it also gives a +20 Magic attack bonus. This makes it the best off-hand Magic attack item in the game, outclassing the mage's book and the ancient wyvern shield (+15). The ancient wyvern shield offers more defence against stab, slash and magic attacks when fully charged, but penalises ranged defence, unlike the arcane spirit shield.

Like the other spirit shields, it also gives a small Prayer bonus and has no offensive penalties, making it suitable for all styles of combat. Its substantial Magic attack bonus, however, makes it most suited for mages.

Trivia

 * The arcane spirit shield is the only sigil spirit shield that doesn't have a passive effect.