I thought the entry for Arcane Arrester says you can't combine it with Magical Resistance?

It does. Someone felt that the threesome would be too awesome, I suppose.

Anyway, background count doesn't alter counterspelling, so a character who has counterspelling naturally or via obtaining the Magical Guard Power is just that much more awesome with Hazing.

So it does(that'll teach me to post before I get fully awake). Well, no Magic Resistance then.

It is not circumstantial. All base damage would be halved. To make comparisons, I'll do arrestor vs rtg 4 magic resist.
Assuming all stats at 3 for the guy with the qualities.

Manabolt:6 6 hits by magician
Arrestor, 1 resist hits, 5 net hits. Base damage halved to 3. Total damage 8 instead of 12.
Magic resist, 2 resist hits, 4 net hits, Total damage 10.

Flamethrower:6 6 hits.
Arrestor, 1 dodge hits, 5 net hits. Base damage halved to 3. Body + Armor resist 2 hits (6 armor), 6 damage instead of 12.
Magic resist, 1 dodge, 5 net hits. Body + Armor + Magic resistance 3 hits. 8 damage instead of 12.

Even lower force, arrestor is still better.
Manabolt: 4 4 hits by magician
Arrestor, 1 resist, 3 net hits. Base damage halved to 2, Total damage 5.
Magic resist, 2 hits, 2 net hits, Total damage 6.

Flamethrower, 4 4 hits.
Arrestor, 1 dodge, 3 net hits. Base damage halved to 2. Body + Armor resist 2. 3 damage reduced to stun.
Magic resist, 2 hits 2 net hits. Body + Armor + resist 3 hits. 3 damage, still physical.


Now, really low force, resistance wins.
Manabolt: 2, 2 hits.
Arrestor, 1 resist, damage halved to 1. Total damage 2.
Resist, 2 hits, spell resisted, no damage.

Flamethrower: 2, 2 hits
Arrestor, 1 dodge, 1 net hit. Damage halved to 1, Body + Armor, 2 hits, damage resisted totally.
Resist, 1 dodge, 1 net hit. Body + Armor + Resist, 3 hits, damage also resisted totally.


Arrestor is clearly better than resistance.

Half base damage vs. spells. Yes, it is a circumstantial reduction. Further, the reduction amount depends on the spell's Force.

Now, Arrester is better against Combat spells vs. Magic Resistance. Without the adjusted Force limiting Hits, however, it overall is not better, because Magic Resistance protects you against Manipulation, Illusion, Negative Health, & some Detection spells. Arrester protects you against Turn to Goo & Petrify.

Once again, unless Arrester limits Hits to the adjusted Force, it is far to expensive. If you simply reduce the cost, it is still not nearly as useful, & not likely to be taken.

With it limiting Hits to the adjusted Force, it is worth 25 points, but due to the downside of also functioning vs. beneficial spells, it is far from a must-have. The only character I would ever take it on is one specifically designed to be heavily magic-resistant.