Rules as written: the subtleties of "can see" you're reading into don't exist. Whether you "can see" something mechanically means "you have line of sight to it." This heavily implied by the Player's Handbook, and finally made explicit in the Rules Compendium's section of Line of Sight on p106:
A few powers do require a user to be able to see a creature to target it, however. For instance, a power might specify that it targets "one creature you can see." In other words, the creature must be within the user's line of sight.
So the Warlock's curse simply refers to those enemies to which you have line of sight. You have line of sight to someone simply if you can trace the corners of your square to the corners of their square, and that's it, so whether you're covering your eyes doesn't change anything. Since covering your eyes doesn't change your line of sight, the only RAW answer is: nice work, smart guy — you still have line of sight to all the other monsters.
The rules are built on the assumption your characters are generally trying to look around and be aware of their surroundings, and not pulling these tricks. If it doesn't make sense why you can't use a spyglass to affect who you can see and change your line of sight, it's because you've exited rules territory, and at that point the rules aren't expected to make sense.
The RAW way to eliminate line of sight is to manoeuvre around obstacles and eliminate it. So that's what a Warlock wants to do, if they want to get creative with limiting their Curse targets by vision.
How can this make sense or be explained in interpretation or story?
Before this, there's a big principle of D&D 4e to understand: it prioritises balance and fun mechanics above rules making total sense story-wise. Thus the mechanics do not bend or adjust to what makes sense simulation-wise: powers and features do what they say, and it's up to the story to make sense of that. There is no attempt to simulate things realistically, which is a major point of contrast to previous editions, and a contributor to D&D 4e dismantling the Omnipotent Wizardry Tier of classes.
So, given this 4e ethos, the axiom is that Warlocks can only curse the nearest enemy in line of sight (whether the Warlock's covering an eye or not). As BESW points out, this is a fun and interesting part of the Warlock's tactical decisions. It's up to the Warlock's player and their companions to make sense of why this is the case, which could be a pretty fun opportunity to flavour your Warlock or their magic.
- It may be the nature of the curse. It refuses to be cast any other way, or picks its own target.
- The Warlock may be capable of casting it another way, but have good reason not to. Doing so may lead to very, very bad juju. Doing so might be violating their pact.
How would I handle someone trying to do this?
How we'd handle it in our own games is a matter of opinion and style. Some would allow it (especially if they're a fan of rule-of-cool and it was cool). Others would ask the Warlock to put the telescope away. I'd probably do the latter, so as to not have the small headaches that might follow from wandering outside the rules into simulationist territory.
It is a fun feature for a Warlock to deal with (having played one myself), and truthfully, having read how BESW would approach this, I'd do as he does.
If none of the backgrounds in the Player's Handbook (p. 124-141), or the Sword Coast Adventurer's Guide (p. 145-154) seem to fit you, discuss with your Dungeon Master(DM) a custom background. Once you determine why none of them fit, your DM may be able to show you how one does fit, or help you create a custom background as explained on page 289 of the Dungeon Master's Guide. There is also the "mix and match" approach (p. 125 PHB) where one swaps features between backgrounds already presented to get a custom background fit for your character. Work with your DM (it's a collaborative approach) to get the fit "just right" for your character and the campaign.
Each background comes as a package. It typically includes:
- A background name
- A description
- Two added skill proficiencies (on top of any you chose from your class)
- Tool and/or language proficiencies1
- A starting equipment list
- A feature.
Read through a few of the already created backgrounds to get an idea how these fit together.
I'd suggest comparing the Sailor, the Criminal, the Folk Hero, the Guild Artisan, the Sage, and the Outlander to see how different packages are assembled. When you and your DM mix the elements together for your background, that will keep it consistent with the Background feature at your table for those who picked one from the pre-built backgrounds.
The Personality Traits, Ideals, Bonds,and Flaws you can pick and choose from all of the various brief descriptions already in the Players Handbook, or try your hand at making a few in your own words. Whatever you do, work with your DM so that it all fits into the campaign world you are going to play in.
The point of this, of establishing a background, is that you enter your adventuring career as someone with a past, a past that for one reason or another led you to the adventuring life. This step in character creation helps you flesh out your role and gives you some touch points for role playing. Role playing evolves into the story of your character. As the story grows your character becomes some kind of hero in the context of the game world.
I have found that writing a brief story of "how I got here" helps me get a grip on who the character is. The background is a great starting point for beginning that "how I got here" story.
1 Tools and languages (pick a total of two) are part of the mix and match approach. Using the examples of Acolyte, Criminal, and Noble...
Acolyte: Skill Proficiencies: Insight, Religion
Languages: Two of your choice
Criminal: Skill Proficiencies: Deception, Stealth
Tool Proficiencies: One type of gaming set, thieves’ tools
Noble: Skill Proficiencies: History, Persuasion
Tool Proficiencies: One type of gaming set
Languages: One of your choice
(Source: PHB, Ch 4).
Best Answer
By the rules, no. The Pact of the Chain says:
And the find familiar spell says:
The list of which creatures you can use as a familiar is highly specific, and doesn't include either the Wolf or the Dire Wolf.
That said, some of the options available to a Pact of the Chain warlock are quite a bit more powerful than a Wolf. The Imp and the Quasit are both CR 1 to a Wolf's CR 1/4, with spellcasting abilities to boot, so a generous DM might be willing to stretch a point and let you use a Wolf instead, particularly if it's appropriate for a character. I suspect a Dire Wolf is probably out of the question, though.
There is another potential alternative: If you took 3 levels of Ranger, you could get an Animal Companion, for which a Wolf is an option. Depending on your character, a Ranger might fit as a substitute for Rogue. A character for whom a Wolf familiar makes sense sounds a bit Ranger-ish to me. Only you know what you want your character to be, both mechanically and thematically, so I can't really advise you too much here.