Eldritch Invocation Guide: The Best Way to Use Eldritch Sight in DnD 5e

When it comes to spell slots and their spell list, warlocks tend to get the short end of the stick.

Sure, theoretically you can have infinite spell slots with multiclassing, and everyone loves Eldritch Blast, but as a whole, warlocks are not quite the spell slingers wizards or even sorcerers are. 

But that’s okay, because what warlocks do get are a ton of powerful features and abilities related to their spellcasting, and eldritch invocations are among the best of these. 

Eldritch invocations are powerful fragments of magic accessible mainly to warlocks (though many are available through the Eldritch Adept feat).

Warlocks get several of these, starting out with two at level 2 and increasing to eight over the course of their 1-20 career. 

As a core feature of the class, there are a lot of options to choose from, and where there’s choice, there’s indecision.

For a more general guide, check out this article, but for this piece we’ll be doing a deep dive into Eldritch Sight, a requirement-free eldritch invocation that allows infinite access to the spell Detect Magic.

What Is Eldritch Sight?

Eldritch Sight is fairly straightforward. It reads:

You can cast Detect Magic at will, without expending a spell slot or material components.

The wording of this is admittedly a little weird; Detect Magic, after all, only has verbal and somatic components. Still, it’s clear what the invocation grants: unlimited access to Detect Magic.

If you wanted, you could cast this all day every day (though you might run into some troubles trying to take rests!).

Is unlimited Detect Magic worth it though? To answer that question, let’s look at the spell itself.

Detect Magic

To start off with, here’s what this 1st-level divination spell does: 

  • 1 action to cast
  • A range of self
  • Verbal and somatic components
  • Lasts up to 10 minutes, concentration

The spell allows you to sense the presence of magic within 30 feet.

If you sense magic, you can use your action to see its faint aura around any visible creature or object that bears magic and is within range. You also learn its school of magic, if any. 

The spell ignores most barriers except for 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood/dirt.

This spell can be really useful for spotting magical items that have been hidden among common items or disguised ones (such as magical traps).

It also allows you to get a sense of what kind of magic is at play.

Is that wizard covered in wards (abjuration magic), or do they have some transmutations strengthening her?

Is that magic sword likely to have flashy damage-dealing abilities (evocation), or does it simply detect the presence of goblins? 

5e makes an extraordinary effort to ensure that there are no exploits to make the game unbalanced, so sadly the ability to infinitely cast a 1st-level divination spell doesn’t lead to infinite power. 

That said, awareness is an excellent defense, and simply knowing that some kind enchantment spell has been laid on an NPC can change the course of a game (or, occasionally, derail it). 

Should I Take Eldritch Sight?

Detect Magic provides an undeniably useful resource. Being able to pull Detect Magic to check out your environment at any moment can save your party from a lot of illusions, traps, and other kinds of issues. 

Plus, the ability to cast Detect Magic as much as you want is particularly valuable for warlocks, who have a limited number of spell slots and don’t actually get Detect Magic on their usual spell list. 

Eldritch Sight is a good way to gain access to that spell without being limited by having to spend a max-level spell slot on its simple utility. 

That said… a lot of spellcasters already have Detect Magic and have the spell slots to support its casual use.

Moreover, for classes with access to ritual casting, Detect Magic can be cast without a spell slot if you have 10 minutes to spare. 

Eldritch Sight makes the spell accessible to warlocks and makes it easy to spam.

However, if you already have players in your party with access to the spell, it’s worth asking if there’s an extra advantage to your ability to cast the spell quickly. 

Perhaps one of the uses for the spell below is particularly relevant for your campaign, or you’re the only spellcaster in the party.

In these cases, having Detect Magic might be crucial. However, certain party compositions will make it redundant, so it’s important to coordinate with your friends when picking your core abilities. 

Think about your playstyle before picking this invocation, and check out the ways Detect Magic can play out in game (see below for more examples of this).

If the spell will be useful, that is, if you will use the spell regularly, then Eldritch Sight will be a great pick for your warlock. 

One more note before we get into the more specific ways to use Eldritch Sight:

This is not the only way for a warlock to get Detect Magic through their invocations.

The Book of Ancient Secrets for Pact of the Tome warlocks also allows (more limited) access to Detect Magic in the form of ritual casting.

It’s a slower process, and the invocation is more limited, but this route is also arguably more powerful since you gain access to other ritual spells as well. 

If the Pact of the Tome appeals to you, make sure to consider this invocation as well. Picking both Eldritch Sight and The Book of Ancient Secrets would definitely be redundant. 

Using Detect Magic

Detecting Traps

There are really two types of traps you can detect with Detect Magic: traps that use some piece of magic to harm you and traps that use magic to trigger or hide something that harms you. 

The first type includes all those runes and symbols included in the spell list but also includes any nonstandard magical traps your DM might have thought up.

Remember that Detect Magic detects magic, not the effects of the spells that a character class can play.

Even if a magic item or magical effect isn’t based on any conventional spell or school of magic, it still shows up as something, and that bit of warning (assuming you pay attention to it) can be critical.

After all, you don’t want to be known as the adventuring party that fell for the old disintegrating floor trick! 

The other type of trap mostly involves illusion magic (or maybe enchantment magic) that tries to trick you into taking dangerous actions.

Suggestions spells that suggest you step on this piece of the floor or illusions hiding spike pits and making it seem like cutting the blue wire won’t trigger the explosives can be deadly, even if the actual damage isn’t magical at all. 

You might be immune to magic, but an illusion can still trick you. 

Detect Magic is ideal for spamming in dungeons and other areas likely to be trapped for this reason, and Eldritch Sight allows for the most regular use of it.

Just remember that the rules can be somewhat gray when it comes to illusions. You might know that there’s illusion magic in the area, but that won’t tell you if it’s specifically an invisible creature.

Depending on your DM’s interpretation of the rules, it might not even tell you if a particular object or creature is an illusion (are illusions of objects themselves objects?). 

This ambiguity definitely increases the value of Eldritch Sight for a long dungeon crawl; keeping an active Detect Magic up at all times might be more useful than taking 10 minutes to cast the spell as a ritual when you think you need it. 

Detecting Magical Creatures

It is unclear whether or not Detect Magic can detect inherently magical creatures. There, I said it.

A lot of people have strong opinions one way or the other on this, but I just don’t think that with the rules as written, you can definitively say one or the other.

There’s not enough information on the cosmology, and this will be a case-by-case call. 

Certainly, you should be able to detect creatures being actively summoned by a spell (or at least detect the spell), but after that it gets fuzzy.

I think that creatures sustained entirely by magic, such as elementals, constructs, and the undead, should show up. 

Creatures who are deeply invested with magic, such as dragons, demons, celestials, etc., might regularly show up… or might only show up when using one of their magical abilities.

For everything else, it’s hard to say. Certainly, it would be weird if sorcerers and clerics showed up as magical, but I could also easily see a world where that makes sense. I recommend asking your DM about it.

Assuming you can detect magical creatures (to some degree at least), you can expand Detect Magic’s utility to sensing some kinds of monsters that may be lying in ambush for you, ferreting out certain kinds of shapeshifters, and generally sensing the presence of powerful beings (assuming those beings are already very close by). 

This might break the ability for creatures or your party to stealth though, as a Detect Magic could be enough to alert searchers that something unusual is happening. 

Detecting Non-Standard Magic 

Finally, Detect Magic can be used to spot magic without a specific school. While D&D 5e has dropped 3.5/Pathfinder’s habit of giving every magic item a specific aura, many objects will still fit easily into one of the schools of magic

If you’re an inventive DM or play with one, you might, however, find items with less easily categorizable effects. Detect Magic can help here, maybe more than other less generic detection abilities. 

We’re getting into homebrew territory, but I believe that in-game Detect Magic should represent a character’s ability to sense, investigate, and probe magical effects.

So, maybe the spell doesn’t produce a specific school for your homebrew magic item that lets you travel into someone’s mind and fight their demons in the metaphysical flesh, but it might allow a dedicated character to guess that the spell involves transporting people into non-physical spaces. 

However you end up ruling it in practice, the spell text does allow for some nuance in what exactly it detects and the information the caster gets back.

If you want to use the spell as frequently as Eldritch Sight allows, I strongly recommending talking to your DM about some of the stranger kinds of magic you might pick up on. 

Final Verdict 

The question is simple, should you take Eldritch Sight? The answer is a little more complex. 

Eldritch Sight can be great at any level if you have a need for regular uses of Detect Magic in situations where spending 10 minutes to cast it is inconvenient but you still won’t be in combat (if you’re in combat, please don’t try to use magic to defend yourself). 

That can be a niche situation, and maybe it isn’t worth an invocation for you. On the other hand, that pretty much perfectly describes old-school dungeon crawling where you need to be constantly aware of magical traps.

In older editions, Detect Magic was often a very spammable cantrip, and there were more magic items to cast low-level spells like it repeatedly. 

If you’re dungeon crawling in 5e with a DM used to that style of play, Detect Magic isn’t just handy; it’s essential.

If you are the only caster with Detect Magic in your party or if you’re your party’s only caster, then Detect Magic can be a literal lifesaver.

If you’re in any campaign that isn’t extremely low magic, you’ll have lots of opportunities to look around with the spell, and your party will benefit from the extra information. 

On the other hand, you might only have a handful of invocations and really just need them all for your Eldritch Blast damage-stacking.

At the end of the day, this invocation has a lot of utility, but you’ll have to use your own foresight to decide if Eldritch Sight works for you.