Bastion is a star within the Constellation the Lord in Elder Scrolls Online.
This was added in Update 6 with the Champion System. It increases the effectiveness of damage absorbing effects by [x]%. You can put 100 Champion Points into this passive ability for a maximum of 25%.
Bastion improves shields you initiate. So if you have a shield that goes over other players, it will improve it for them too. Skills affected included:
With each point invested, the increase in effectiveness of damage absorbing effects diminishes. That is to say, for the first 10 CP invested, you would gain a 4.78% increase in your Effectiveness However, the next 10 CP spent (making a total of 20 CP spent), will earn you only 4.26% more Effectiveness. This is 0.52% less than the increase gained in the first 10 CP.
As such, spending just 37 CP into Bastion will already gain you a 15.1% increase in the Effectiveness of damage absorbing effects. This means you will have gained 60% of the Maximum increase possible (which is 25%) by spending just 37 out of the total of 100 CP. Therefore, beyond this point, the increase in Effectiveness received per 1 CP used is very small and not as worthwhile.