Effects of a blessed weapon?

[nsruf]

Just a minor thing I noticed: spells like Bless Weapon or Magic Weapon (if cast by a cleric) are said to make a weapon "blessed, which means it has special effects on certain creatures" (quote from PHB).
However, I am not aware of any mention of such effects in either the MM or DMG. Am I just blind or did they forget to put this in?

 

[Dr. Zoom]

You find it in some of the demons and devils descriptions, and the rakshasa.

 

[nsruf]

Thanks! I was expecting it to work on undead, but it seems to be less common, then.

 

[Dr. Zoom]

Right, I don't know of any undead creature that is particularly vulnerable to a blessed weapon, although there might be one or two. Also, one of the designers said that although the blessed weapon does not have many uses, it is still there ready to be employed by new creatures, both official (MM2) and home-brewed. So you could create a modified or new undead creature that in some way requires a blessed weapon to hurt it or destroy it.