How do we kill what we can't see?

Question

We are a large party, all level 6: Storm Sorcerer, Shadow Sorcerer, Lore Bard, Dual wielding DEX fighter, Thief, Moon Druid, Forge Cleric

We are repeatedly running into a problem encounter, that we've had to run from or take NPC losses, only killing less important enemies.

It's a group of hobgoblins all mounted on wargs or greatwargs. Their leader has heavy crossbow with 3 shots (and melee weapons?). Their mage will turn invisible and get off warg, throws level 4 spells at us. And there's two more mounted with lances and greatswords as a buffer.

Now as a Forge Cleric I have massive AC. If the mage wasn't around I think we could take them. DM seems to do lots of things that bypass my AC, fireball, ice storm etc..

I want to close the distance but they stay back and I don't have great range. Everything seems to pass my spell saves too. Fairie Fire is a good idea but Bard doesn't have it, and when Druid missed a session DM said she "vanished" so I don't know when she'll be back.

I do believe I understand 5E stealth rules. My DM didn't understand and may still disagree. He is coming from other editions and is Homebrew happy. It's a point of friction.

What are good strategies? How do we get this invisible mage so we can make with the heroics, and story progression?

Answer 1

Prevent it from going unseen in the first place

The most straightforward way of hurting something that is invisible is by preventing it from going invisible in the first place. If the mage is within 60 feet of you when it casts Greater Invisibility, both your Bard and the two Sorcerers can attempt to counterspell him. This is by far the best solution, because it makes the mage waste a fourth level spellslot without actually going invisible.

If your sorcerers have Distant Spell and don't mind silly gimmicky layering, you could in theory Counterspell them from further away with Distant Spell. While Counterspell's trigger won't double in range, it also doesn't specifically say that you have to counterspell the creature that triggered your casting. So you can have one person prepare "I cast this cantrip when the mage starts casting", and then that becomes the second person's trigger for counterspell, at which point you can metamagic it to 120 feet and counterspell the enemy mage from a larger distance, but this seems extremely silly and rulebendery. Alternatively, your DM might just rule that Distant Magic simply works by default with Counterspell, changing it to 120 feet.

If, however, the mage is too far away, then you have several characters who are good in AoE spell damage. Every time the mage takes damage, they'll have to make a concentration check to remain invisible. Simply throw all your AoE spells in the spot where you last saw the mage, capture as many of the other Hobgoblins in the blast as well, and go from there. As soon as the mage fails their save, they'll be revealed again.

Faerie Fire would not really help you because it's vastly outranged by crossbows and fireballs (it has the same range as counterspell), so there's little reason for the enemy mage to come in range of that spell if they weren't already in range of the counterspell in the first place. It might be useful if you have Distant Spell and are then able to get him in the cube from 140 feet away, but it's vastly inferior to preventing them from going invisible in the first place.

Answer 2

Remember that unless the hobgoblin takes an action to hide, you know which square it's in(PHB, 291) and also discussed in this question. Weapon attacks don't, in general, require a visible foe. A number of spells require you to see the target, but a few don't, like Guiding Bolt(PHB, 248), which I bet you have.

"But those are rolled with disadvantage, Exal!" True! But, firstly, there are a number of ways to get advantage, taking it to normal (even just finding a way to heavily obscure yourself). If your rogue's anything like mine, he's dashing behind cover and Cunning Action-Hiding every Pelor-damned fight. If your fighter or another dude can get next to the invisible blighter, attacking at normal with an ally adjacent is enough to get that sweet, sweet Sneak Attack damage.

Secondly, invisible creatures get no advantage against spells with saves! You have two Sorcerers, is it possible one has a spell requiring a save rather than an attack roll?

Answer 3

Maybe killing isn't what the DM has in mind

I see 2 issues, first is that Greater Invisibility only lasts a minute, if this mage is spending the first turn in combat casting it on themselves, then your team has chance to take them out or at least do damage. If they start invisible, then that sounds like your DM isn't 'playing fair' because a group of snarling wargs are getting close enough to you that the mage feels safe casting the spell without wasting duration, but you aren't being given chance to hear them approach.

Now I know I should be giving your DM the benefit of the doubt here, but with the description you gave me I don't, which brings me onto the real answer:

This encounter is above your level

Having to face opponents with 3 attacks, high manoeuvrability and spells of 4th level (Multiple spells by the sounds of it) gives me reason to think that either your DM is setting up encounters you should run from (teaching you that you can't always win, or setting up a recurring enemy), or calculating CR wrongly.

That being said you have survived this fight, so you must be doing something right.

How to win (?)

Ask your DM (pointedly) how close these hobgoblins are getting on their loud snarling wargs before you can hear them, and how they know where you are before you can hear them coming. You should really be getting a chance to at least take cover.

So ideally you convince the DM of this, and start in cover, even setting an ambush if you are lucky. The hobgoblin mage shouldn't start invisible, and I would call shenanigans if they did EVERY TIME, because that is breaking the action economy by using a short term buff out of combat, which I am guessing your party isn't being given chance to do.

Then focus fire, you should, by the rules, know where the invisible mage is, so unload on it. Drop you own AoE's like Fireball, or Faerie Fire so it can't benefit from invisibility.

If you have to run after this then do so, and maybe the next encounter will be easier (unless hobgoblin mages grow on trees), or maybe you can turn and track the hobgoblins back to their camp and get the drop on them. Packs of wargs tend to leave easy to follow trails.

How to win: part 2

Play smart, work out how they are tracking you and how they are moving. Move slowly if you can and lay traps as you do so, tripwires, snares, holes and pits, then stay in that area. Hopefully the pack of wargs will run into the traps and you can get the drop on them as they recover.

Answer 4

Dispel Magic doesn't require you to see the target

Unless the mage has spent its action Hiding, you know where it is. Cast dispel magic on it. Dispel magic has a range of 120ft, so if the mage is close enough to fireball then its close enough to be dispelled.

Alternatively, Ready dispel magic for when the mage casts a spell.

Neither does fireball :-)

Invisibility provides no protection against area attacks.

Answer 5

Note: The following assumes that the core issue is that the location of the mage is unknown to the party, rather than simply that attacking someone that is invisible causes disadvantage. Knowledge of the mage's location makes these strategies less desirable, favoring things AoE attacks instead.

During battle:

Control the battlefield in ways that break the mage's sight lines and give options for detecting the mage that don't rely on seeing it.

First off, the other answers are great and are totally viable approaches (Theik's in particular would be my first choice, as it's a straightforward counter). This is simply an additional option.

The first and most important thing to do is to frustrate the mage's ability to damage you. Spells are powerful and effective, but only a limited number are typically available during a fight and they require line of sight to be effective.

If your characters can prepare or find and exploit areas of total cover (like terrain features, spells like Fog Cloud, and similar) you can really disrupt the mage's ability to target your party with spells. AoE spells can still sting, but if you have cover over a larger area (like hiding in a trench, or running around behind a wall) even those can miss. If your party is level 6, this enemy is unlikely to have a huge number of spell slots, so they can't afford to miss very often and remain effective.

For that matter, buying a few more potions of healing beyond your normal kit would give you more ability to be hit by those spells, and once the mage uses those spell slots they're gone. Once the spell slots are gone, it won't matter much if the mage is visible (or even present, unless there's more to them than the magic).

The next thing to consider is that you have more options for determining a creature's location than just looking at it. How, specifically, you locate it instead depends on specific resources you may have and what the terrain is like. If you can cover a stretch of the ground in sand, mud, gravel, broken glass, water, or something similar, then even an invisible creature will give signs of its passage. Those might be footprints, sounds, or something else. Even if the mage can try a Stealth roll, you will have more chances to locate it than you otherwise would.

These two can also be combined. If you can prepare your battleground, or contrive changes to it when you're there, well-placed obstacles blocking sight can be used to create areas where the mage would have to be to target your party well and then those areas can be set up to give away an invisible occupant you'll have done a lot to neutralize the advantage.

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Before battle:

Maneuver

I don't know the pre-combat setup, but do you need to rush in head-on? With a Shadow Sorcerer, Thief, and Druid you've got a lot of options for sneaking and stealthy approaches. A cautious approach capped by the right action (which will depend on what your party can pull off reliably) could neutralize the mage immediately and before combat takes place at all.

I'll especially recommend this as it seems that you've had several run-ins with this group of enemies and seen the same results every time. It's worth rethinking the frontal assault. I can't speak for your DM, but when my players start to settle into a particular battle strategy I give them a few encounters that frustrate it. Just to keep things interesting and prevent my players from getting complacent.