Mostly for defense (especially if you don’t feel comfortable unslotting it yet) but you may also use it for resource return.
It absorbs both spell and physical dmg and returns it to you as magicka. Plus the larger your mag pool, the bigger your shield. You will *DEFINITELY* need it for Starfall on Warrior (vHRC), Rakkhat, and the Valariel add burst (vAA). Remember that it’s damage ABSORBING, so if you’re taking large amounts of damage, it will not last the full 6 second duration. This skill can be buffed by “Bastion” under the Red CP tree, but I don’t recommend that unless you’re really struggling with survivability.
Thank you to Harven for a wonderful little add-on that lets you see different morphs of a skill. Super handy!