Why is this specifically limited to melee attacks? Why can't this be used with a ranged weapon? 

I would assume because your body is being transformed into a magical conductor for the elements listed. Thus, you are touching your melee weapon, allowing the element to flow into it and remain in it during the attack. If it were ammo based, the ammunition wouldn't remain in contact with your body, so it wouldn't gain the elemental damage.

Quote from egwythe37 >>

it says "captures some of the incoming energy, lessening its effect" - is it halved or a certain amount less...? Or is it just saying that?

 Yeah, I'm curious about that too. Is it resistance or you subtract 1d6 damage?

This seems like it would be good for hexblade warlocks but of course they don't get it :(

Might be interesting to see a Sorcerer based gish with the Elemental Spell Metamagic us this to reduce damage from an attack and then use a different damage type as many creatures are immune or have resistance to damage types they use.

If a creature casts Hellfire orb(deal necrotic, and fire damage) would I only take half fire damage, but still full necrotic?

You have resistance. 

But combined with call lightning...

not against fireball it wont. 

Quote from Qwarg >>

If a creature casts Hellfire orb(deal necrotic, and fire damage) would I only take half fire damage, but still full necrotic?

 Yes.

wow

Resistances do not stack RAW.  But if you make your save and absorb, then you only take quarter.

Is the amount of damage you receive reduced by your 1D6 roll?

Is it only for melee attacks, or ranged as well? Seems to be only melee

Generally no but your dm can allow it which would quarter it overall up to the dm

Quote from egwythe37 >>

it says "captures some of the incoming energy, lessening its effect" - is it halved or a certain amount less...? Or is it just saying that?

 Its halved because it also says it grants you resistance for the the triggering damage

Quote from LEGOLOSS >>

dis spell bully me, I want it as a cantrip but its still first level!!!

 

 Probably because it would be overpowered as a cantrip

Quote from egwythe37 >>

it says "captures some of the incoming energy, lessening its effect" - is it halved or a certain amount less...? Or is it just saying that?

 It says you gain resistance, so the damage is halved.

That would not work as you only have 1 level in Warlock, so you cannot cast it using a 5th level slot.

Hi mods, I believe this is missing some of its descriptive text

I know it's a supposition, but if you are attacked twice from 2 different types of damage and use this to protect you, what will be the outcome type of damage of the melee attack