[Velusion]

The following is just my expereince with AC. Others might be able to clarify/correct me.

I'm pretty sure that if your chances of getting pegged by a horror with AC depends on how many gems you spend cast/forging. It doesn't matter if it's mixed blood forging - in only matters how many gems you are putting into it (the amount of slaves doesn't factor into it). Gems saved via forge bonus/site bonus don't factor into the chance - only the actual amount of gems you spend.

Having Blood Magic doesn't matter.

All non blood paths are treated the same.

When you say safe do you mean what is the maximum amount of gems you can spend and be safe? Actually you always have at least a small chance of being attacked if you spend any gems. I'll usually feel pretty safe if I spend less than 5 gems on an item (5%). 5-10 makes it unlikely (15%?) you'll get a horror. 10-20 means you have a good chance of attracting one (45-50%?). Anything over 20 will almost always call a horror (and a Doom Horror most likely).

That all being said I'll NEVER risk a powerful/imporant caster if AC is up (or I think it will go up) unless I don't have a choice. Even if you script to defend yourself against a horror - weird things happen (like being attacked twice) and it just isn't worth the chance of losing a vital mage for a small item/spell.

A whole separate thread could be devoted to the best way to fight/avoid the horrors you've attracted.