UOGuide.com said:
Slayer Opposites
In a mechanic of the game that was long thought dormant but not, each slayer type has an "opposite." Wielding a slayer type against its opposite will cause the attacker to take more damage then he or she would otherwise. For example, using an Undead Slayer against a reptile will cause the attacker to take additional damage from the reptile.
Only monsters from the
opposite group will be devastating for you.
UOGuide.com is having a little trouble for me right now, maybe server or connection problems. I used the web archive:
Slayer - UOGuide
Beware:
I think the information about reptiles quoted above is
WRONG! It says reptile, but I as far as I remember the opposing group is 'Humanoid', not 'Reptile'! I would correct that right away in UOGuide if it wasn't down right now :-/ Good thing about UOGuide is: it is a Wiki. 'Anyone' can edit there (I think you have to be logged in with an account, though).
I found a
Stratics page about slayers:
UO Stratics *New* | Slayer Weapons
Stratics says the opposing group is 'Humanoid' just as I thought.
uo2.stratics.com said:
Each of those groups have an opposing group. (i.e. Humanoid vs. Undead)
- The opposing group will do double damage to anyone wielding the Slayer.