My mental image. What if this guy were, you know, a protagonist?
I've always liked heroes that have the courage and ability to wander in dark places. This ranger archetype focuses on that thematic element. (I've just this moment learned that there's a group in the Pathfinder setting called the Lantern Bearers. This is unrelated to that group.) At the same time, I'm also interested in addressing, in a piecemeal way, some of the mechanical shortcomings of the Ranger class. Whether I've addressed thematic shortcomings is more a matter of personal taste. Also, you probably know by now that I'm not shy about references to Tolkien; Aragorn fighting with sword and torch at Weathertop is another point of reference in my imagination here.
Lantern-Bearer Ranger Archetype
A Lantern-Bearer ranger guides travelers in the darkest places, when all other lights go out. Their sturdy brass lanterns may be a weapon in the hand or a way to bolster their allies' morale.
The Brass Lantern
At 3rd level when you choose this Archetype, you receive or fashion a sturdy brass lantern, and modify it according to the traditions of the Lantern-bearers. (You may modify magical lanterns in this way without damaging them.) You may treat the brass lantern as a light finesse weapon that deals 1d4 bludgeoning damage. While your lantern is lit, you may:
Deal additional damage with it by expending spell slots. When you hit a creature by using the lantern as a weapon, you may expend one ranger spell slot to deal fire damage to the target, in addition to the lantern's damage. The extra damage is 2d6 for a 1st-level slot, plus 1d6 for each spell level higher than 1st, to a maximum of 5d6. The damage increases by 1d6 if the target is a beast, a monstrosity, or an undead.
As a bonus action, place the lantern on the ground, or hang it from something high up. Once placed in this way, any creature other than you must roll a Strength check against your saving throw DC to move the lantern. Expend a first-level spell slot to cast bright light in a 10-foot radius. For each spell level higher than first that you expend, its radius extends another 10 feet. Allies within this radius gain advantage on saving throws against the charmed and frightened conditions, and gain resistance against cold damage and necrotic damage. Creatures that take a short rest in this area regain two additional hit points per level of the spell slot used for each Hit Die they expend. These effects end if you move the lantern or wield it as a weapon, or at the end of 8 hours. The lantern provides dim light, but no other effect, in an additional radius of equal size.
Starting at 7th level, you gain two mystical abilities. Once you use either of these abilities, you may not use either of them again until you complete a short or long rest.
As part of a melee attack using your lantern, you may attempt to dispel any magical effect causing the space your target stands in to be lightly or heavily obscured. This functions as a limited application of dispel magic, and does not cost a spell slot. Alternately, you may use this effect as an action without making an attack.
As a bonus action, while standing in a heavily obscured area, you may teleport to the edge of your lantern's bright light radius, as long as it is within one mile.
A Light Bright and Pure
Starting at 11th level, your brass lantern becomes all the more potent.
When you make an attack using your brass lantern while it is lit, it deals 1d8 bludgeoning damage and 1d8 fire damage.
When you set the lantern in place and empower it by expending a spell slot, any hostile creature of the beast, monstrosity, or undead types takes damage equal to 2 per level of the spell slot you expended if it starts its turn within the lantern's bright light.
Starting at 15th level, when you or an ally cast a spell or channel divinity to heal a creature within the bright light of the lantern, you may designate up to two additional targets that are also within the lantern's bright light. This effect can ignore normal range limitations for healing effects, such as the touch range of cure wounds. Once you use this ability, you may not do so again until you complete a short rest. For healing spells and abilities such as mass heal that allow the caster to distribute a pool of healing energy, Healing Light instead boosts the overall pool of points to be distributed by 10 per spell level that the ranger expended to place the lantern.
Probably everything here needs some amount of explanation. First off, I wanted the lantern to operate about equally well as a weapon and as terrain modification, so I had each function improve at three of the four archetype ability points. I think both options are situationally useful, though if you're all archery, all the time, then only the ability to dispel light or heavy obscurement is likely to matter to you.
The Brass Lantern ability at 3rd grants a slightly diminished version of a paladin's Divine Smite, because I think that the lack of a super-straightforward way to turn spell slots into damage (hail of thorns and ensnaring strike notwithstanding) is a substantial part of the ranger's shortcomings. I toned this down by a die size and flipped them from radiant to fire (a damage type with much more common resistance or immunity) to acknowledge that it is treading on the paladin's toes, and thus avoid completely stealing that thunder.
The second ability of The Brass Lantern is a big deal - that's a lot of separate boosts. I could probably take out any two of those effects and still have something people would want to use situationally. Here too I wanted to treat spell slots as a scaling benefit; the ranger doesn't have tons of slots to spare, so I feel less bad about giving an individual slot a lot of bang for its buck. I also liked the idea of the lantern improving a party's short rests. Well, I like the idea of improving long rests too, but nothing came to me immediately for a sane way to handle that.
Shadowed Paths's first ability is about giving the ranger some way to handle supernatural darkness, even in a limited manner, and also to encourage the ranger to keep the lantern in hand. The second ability points to the "stride in out of nowhere" mystique of the ranger. It's a little complicated to set up, but when it works, it should be a handy mobility boost. Also, you can go explore while the rest of the party relaxes, and as long as you don't get caught out in the open or go too far, you can get away.
A Light Bright and Pure is about boosting damage output in melee, paralleling Improved Divine Smite for 11th level paladins - whatever the other problems, the 11th level Hunter's two Multiattack options won't come up often enough to compare favorably to an always-on 1d8 extra damage. At least Bestial Fury is a clear damage boost within its own context, even if it doesn't bring them up to par.
The second half of A Light Bright and Pure is about making the terrain untenable for some creature types. As with any type-specific power, it might not come up often enough to be good, but I figure that 75% of D&D campaigns use undead heavily, and any time you get to use this against beasts or monstrosities is just a bonus. I initially set this ability at three points per spell level, but backed it off to two per spell level after more thought - it's meant to dissuade, not be a fight-winner in itself.
Healing Light is the one ability that isn't two abilities. By this point I figure I've given good toys to both types of Lantern-Bearer. I don't want to really shake up their gameplay loop with a 15th level power, or I run the risk of players looking at the whole archetype as "but 15th level is when it turns into the thing you wanted to play all along." The point here is to close out by emphasizing the Lantern-Bearer's leader-y side, whether they're boosting their own healing spells or making the primary healer's life better. I created a separate handling for healing-pool powers to avoid confusion, and to stop mass heal from suddenly being 2100 points of healing throughput.