Woo-hoo! Heroes of Horror preview!!

[Mouseferatu]

THAT, however, points to a need for the DM and Players to know each other, how each other is likely to react, and to have a working degree of trust that such changes are not "just to screw us over". NO rulebook can make the Player Characters safe when that trust is not there.

Worth quoting, and expanding on.

One of the bits of advice we offer on running a horror-based campaign is that it requires trust and cooperation between players and DM to make it work. To put it bluntly, you've really got to be friends for this. If players aren't willing to put a substantial amount of trust in the DM, or if the DM just wants to "stick it to" the PCs, horror may not be the best genre for you, at least not in the long-term.

 

[BryonD]

I do not recall anyone mentioning blind-siding the players before.

Obvious things generally do not require mentioning.
I consider it pretty obvious that a player running a paladin will assume that immune means immune. Dropping in an ability that chnages that without letting the player know ahead of time would be blind-siding them.

I think that would be bad.
Perhaps we disagree.

However, I am of 2 minds on this. On the one hand, I generally publish all house and variant rules in a document I distribute to my players. Any books I draw from they are welcome to read (though I am reluctant to loan out my copies, as I may need them between sessions to prepare). I try to avoid any "oh, by the way" rules.

On the other hand, there is a legitimate argument for the DM having a need to occasionally surprise, even "blind-side", the PCs. This is especially true among more experienced gamers, who tend to be more familiar with the rules and who (sometimes) NEED shaking up. THAT, however, points to a need for the DM and Players to know each other, how each other is likely to react, and to have a working degree of trust that such changes are not "just to screw us over". NO rulebook can make the Player Characters safe when that trust is not there.

Keeping the players on their toes is one thing.
But, IMHO, meta-game lying is just bad DMing.
And to let a player operate under the false assumption that their abilities work as described is just that.

 

[BryonD]

Worth quoting, and expanding on.

One of the bits of advice we offer on running a horror-based campaign is that it requires trust and cooperation between players and DM to make it work. To put it bluntly, you've really got to be friends for this. If players aren't willing to put a substantial amount of trust in the DM, or if the DM just wants to "stick it to" the PCs, horror may not be the best genre for you, at least not in the long-term.

Exactly.

And if I as a DM allow a player to expect immunity to be immunity and then drop an expection on them, then I have completely violated that trust. That is really my whole point here.

There are plenty of ways this feature could work. But there are ways it could lead to disruption of the fun as well.

 

[Snapdragyn]

OMG, can't believe we all missed this until now....

There are exactly 13 monster entries (creatures & templates) in HoH. Hehe, shades of the double-entry deja vu power in XPH.