Is an out of sight enemy a problem for Warlock's Curse?

Question

My players like to turtle in corridors, fighting enemies in sight before heading into the room. This often means the Defender is on the door, followed by several ranged characters. This also means the warlock isn't always looking at the whole room while cursing people.

Now, a Warlock's Curse can only be cast on the nearest enemy, and needs LoS.
There are two enemies in the room. NearNuisance is near to the wall where the door opens, out of sight of the warlock. FarawayFool is at the opposite side, fully in sight and farther than the first one no matter how you want to count distances (shortest path around walls or as the bird flies).
For simplicity's sake, let's say no hiding is involved and nobody is cursed yet. Walls block line of sight as well as line of effect.

The warlock player would want to curse someone. NN is Out of Sight. FF is not the nearest.
...but he's the nearest he can see / he's aware of.
I'd like to know what happens, by the rules, in these cases.

1. Nobody has ever had line of sight on the nearest enemy. Yet the encounter was "activated" and everybody knows everybody's position (since NN is not hiding).
2. Another PC has LoS on NN and tells the warlock there is an enemy.
3. Another PC has LoS on NN and tells the warlock the position of NN.
4. Another PC has LoS on NN but nobody tells the warlock (is this bad metagaming?).
5. NN was in sight of the warlock, then dashed out of sight of everyone before the warlock could act.
6. NN was in sight of the warlock, then dashed out of his sight. Somebody still sees it and tells the warlock where NN is.
7. NN was in sight of the warlock, then dashed out of his sight. Somebody still sees it and stays silent.

I'm also interested in knowing in which cases we fall in (2 or 3? 5 or 6?) if the warlock makes a perception check and notices the presence of the enmy itslef. Does it also know the position? Can he choose not to roll the check to avoid knowing?

Answer 1

No, out-of-sight enemies are not a problem for a Warlock's Curse (unless, y'know, an out-of-sight enemy is the one you want to curse). Let's review the first sentence of the Warlock's Curse, which is the only one specifying who you can target:

Once per turn as a minor action, you can place a Warlock’s Curse on the enemy nearest to you that you can see.

In other words, you can curse the nearest enemy out of those enemies you can see. It is not "the nearest enemy to you, if you can see them." If there's a nearer enemy who you cannot see, ignore them completely for the purposes of determining a valid curse target.

You need Line of Sight to them, but not Line of Effect. You need to have Line of Sight at the point you try to curse them, which will be on your turn since it takes a minor action.

So, to your situations:

In all cases, FF is the only valid curse target. Out of all the enemies you can see, they're also the closest (kinda unavoidably), so you can curse them.

• In case #1, NN is not in sight, so they're ignored for determining curse targets.

• In cases #2-4, it doesn't matter if someone else can see NN. FF is still the only one the Warlock can see, and is thus the only valid curse target.

• In cases #5-7, it doesn't matter if NN was, at some point, in sight. If they're not in sight at the time of casting, FF remains the only valid curse target.

You ask about the impact of the Warlock making a perception check to realise where NN is. This isn't an issue in these scenarios. According to the First Premise of Hidden Club, the Warlock already knows exactly where NN is, even if they're around a corner, unless NN is Hidden. If NN is Hidden, go ahead and try to discover them, because it has no effect on who you can curse in these scenarios.

Answer 2

"Line of sight to the enemy's square" is different from "an enemy that you can see". The warlock's curse description says it requires an enemy that you can see; so a hidden or invisible creature cannot be targeted by this power. Line of sight is implied. There are other ways to curse that get around line of sight, for example eyes of the vestige which needs line of sight from the target to the secondary target (although it still can't be invisible). There is a daily that curses creatures adjacent to the creature targeted, in which case no visibility needed.

During the scenario you created, you mentioned awareness -- awareness of a creature, or awareness of a creatures location (invisible / hidden / view obstructed, but know which square he's in) allows you to know which square you'll need to target, but not give you either line of sight to the square nor allow you to see a creature.

So the best example would be a creature in front of you that is hidden from you, but not to your friends. You know exactly which square to target, but still cannot see it, and thus cannot curse it. Unless you roll a successful perception check to remove the hidden condition and the creature only had partial cover or concealment. Nothing changed but your ability to see the creature, and now you can curse the creature.

And yes, you still need line of effect to place the curse (you always need line of effect unless the power / ability / keyword says different). However you don't need line of effect for your pact boon to trigger when the creature dies. However other powers and effects that take advantage of your curse (to do damage, for example cursebite) would require line of effect from the origin square.

EDIT: Ech. I just realized the full extent of the question asked and thus realized I wasn't answering the right question -- The accepted answer is fine. I was wondering why dopplegreener's answer didn't answer my questions.. :). But the line of effect line confused me -- I assume he means line of effect is not needed for determining 'closest you can see'. You still need line of effect to the actual curse target.