I'm idly doodling a 5e sorlock for a very specific thematic mix of subclasses over here, and while I was doing that I was amused to realise that sorlocks can give you a very fun mix of metamagic, invocations and feats that’ll get you a 1200ft range spell.
Specifically, as one might guess, a 1200ft range eldritch blast.
You start out warlock, and you take the Eldritch Spear invocation, which says thus: “When you cast eldritch blast, its range is 300ft.”
So now you have a cantrip with a 300ft base range.
Then you take the Spell Sniper feat, which says thus: “When you cast a spell that requires you to make an attack roll, the spell's range is doubled.”
So our 300ft eldritch blast is now a 600ft eldritch blast.
And then, with your sorcerer levels (or the metamagic adept feat, if you don’t want to multiclass), you take the Distant Spell metamagic, which says thus: “When you cast a spell that has a range of 5 feet or greater, you can spend 1 sorcery point to double the range of the spell.”
So you can spend 1 sorcery point per casting to turn your already 600ft eldritch blast into a 1200ft eldritch blast.
Now. Are there likely to be all that many situations where it’s useful to be able to shoot someone the bones of a quarter mile away? With a cantrip? Probably not. For a start, they might be getting slightly difficult to see at that range. This is more of a ‘cool once-off trick’ than a generally useful thing to sink multiple levels and at least one feat into.
But hey. That one time an enemy spellcaster is trying to escape using the fly spell, it’d be really damned funny to force a concentration check from 1200ft back, just to see if they get to stay in the air. Heh.
And the advantage of it being eldritch blast specifically is that eldritch blast generates multiple beams as it levels, instead of just doing more damage per beam, and each beam gets its own attack roll. So, like, even if we’re at disadvantage just for sheer range, once we get up to three or four beams, surely one of ‘em’s gotta hit?
And if you’re a sorlock with Quickened Spell as your other metamagic, you can also quicken a levelled spell to do something else actually useful on the same turn. In case anyone objects to you wasting turns trying to take potshots at the speck on the horizon.
IDK, the possibility just tickled me, I guess.