My players are soon going to fight against a very high-level human champion of Nurgle. Since they are all high-level DW characters who just murdered 2 other champions of similar level (one Khornite and one Slaaneshi), the Nurglite is searching for any advantage he can find.

In Tome of Decay, there is a new weapon quality called "Irradiated", which causes target to test Toughness or suffer 2d10 Toughness Damage.
My question is - how would it affect Marines with or without armor?

Unfortunately, core rulebook only states " At the GM’s discretion,
the Space Marine may ignore or be resistant to exposure
to radiation, depending on the severity."
The Jericho Reach has completely different rules for Radiaton on page 67.
Ark of Lost Souls has yet another version on page 25 (do not read if you are a player for obvious spoilers ).


What do you think? Should Irradiated weapons not be able to harm Astartes? Should they have a re-roll of Toughness Tests? Or perhaps the rules of Radiation from DW should be used instead of BC?

Some of those weapons like balefire guns are so awesome they might actually set ceramite on fire.

In Tome of Decay, there is a new weapon quality called "Irradiated", which causes target to test Toughness or suffer 2d10 Toughness Damage.

My question is - how would it affect Marines with or without armor?

...

What do you think? Should Irradiated weapons not be able to harm Astartes? Should they have a re-roll of Toughness Tests? Or perhaps the rules of Radiation from DW should be used instead of BC?

Well, nothing in ToD says that BC Chaos Space Marines can ignore Irradiated quality - after all it's not just radiation, it's radiation especialy used in weapon. I personally will use Irradiated as written. Just don't forget that Unnatural Toughness in DW give you bonus to Toughness tests (in BC, afair, it only give additional successes if character succeeds)

In Tome of Decay, there is a new weapon quality called "Irradiated", which causes target to test Toughness or suffer 2d10 Toughness Damage.

My question is - how would it affect Marines with or without armor?

...

What do you think? Should Irradiated weapons not be able to harm Astartes? Should they have a re-roll of Toughness Tests? Or perhaps the rules of Radiation from DW should be used instead of BC?

Well, nothing in ToD says that BC Chaos Space Marines can ignore Irradiated quality - after all it's not just radiation, it's radiation especialy used in weapon. I personally will use Irradiated as written. Just don't forget that Unnatural Toughness in DW give you bonus to Toughness tests (in BC, afair, it only give additional successes if character succeeds)

I'm actually thinking about giving Marines re-roll thanks to Melanchronic Organ, if it works for them (I wonder how it would work in case of Salamanders, and Raven Guard may have some problems with it too; it seems that Death Specters do not have it working at all).

And I'm thinking about halving damage because of Unnatural Toughness (basically reducing it to 1d10 instead of 2d10) - some rules in rulebooks say that Unnatural Toughness halves Radiation damage.

BC Marines are weaker than DW Marines for balance reasons (which, if you ask, still does not work too well), but since I like their stronger version more, I think I'll stick with re-roll to Toughness Test and 1d10 Damage instead of 2d10. It's still painful, since Rad Grenades from Tome of Decay give -20 to this Toughness Test and they're not that expensive to a dedicated follower of Nurgle. And every Rad Grenade that causes damage makes it harder for Marine to pass another test, and they ignore Force Fields.

The melachrome organ is meant to protect against like background radiation and such, I'm not sure it would do much for high intensity artificial radiation that\s been weaponized.

On the other hands, your standard DW players may be a little annoyed by getting 2d10 Toughness damage with no save aside from dodging first or second one. No Force Field, Armor, Toughness Bonus, Wounds... kind of problematic.
I mean, Tome of Decay has even worse "Decay" special rule that makes Irradiated a joke, but still, I would like to avoid my players throwing table at me after finally reaching Rank 6 and than being mauled to death instantly by few guys with Rad Grenades.

I think I'll give them re-roll to Toughness Tests for Melachrome Organ and either roll only 1d10 because of Unnatural toughness, or roll 2d10 and reduce by their lowest Armor.

The second is really nice with Corrosive weaponry of Nurgle, I think I'll stick with it, unless anyone has better ideas.

When we ran into a radiation damage conversion issue, we let the marines reduce it by their toughness felling (1).

Lure of the expanse reactor is what we'd encountered.

Well if you look up the history of the destroyers in 40k, they were marines in the great crusade who used irridiated weapons, it says even the users were corrupted by the radiation, so it's bad on both ends.
http://warhammer40k.wikia.com/wiki/Legion_Destroyer_Squad