Resistant is a star within the Constellation The Steed in Elder Scrolls Online.
This was added in Update 6 with the Champion System. It reduces the amount of damage you take from Critical Hits by 33. You can put 100 Champion Points into this passive ability for a maximum of 1650.
With each point invested, the reduction in the damage taken from Critical Hits diminishes. That is to say, for the first 10 CP invested, you would gain a 316 reduction in damage taken. However, the next 10 CP spent (making a total of 20 CP spent), will earn you only 281 more reduction. This is 19 less than the reduction gained in the first 10 CP.
As such, spending just 37 CP into Resistant will already gain you a 996 reduction in the damage taken from Critical Hits. This means you will have gained 60% of the Maximum reduction possible (which is 1650) by spending just 37 out of the total of 100 CP. Therefore, beyond this point, the reduction in damage received per 1 CP used is very small and not as worthwhile.