From Diablo Wiki
The Shield Pylon grants the player complete immunity to damage from all attacks and debuffs.
When clicked the effects of the pylon will affect the player and his allies within the vicinity for 30 seconds. This duration can not be increased by wearing the Gloves of Worship but the Nemesis Bracers bonus "Shrines will spawn an enemy champion" does work when clicking a Shield Pylon. It's not known if this is working as intended or not.
The Shield Pylon features in the following achievements:
| Blessed Art Thou
Adventure Mode/Nephalem Rifts
|10|| Claim the power from each of the following pylons.