In the campaign Peninsula of Plenty, the City of Nace is a fair city. As a fair city, travelers from far and wide come to purchase things that otherwise cannot be found. The main products sold are magical plants and herbs for the creation of healing and restorative potions. Some of these plants can also be used to make high quality inks for mundane and magical scrolls.
The garden where these plants grow has been magicked to allow production all year round. Since the gardens are very nearly in the center of the city and have virtually zero physical defenses, the druids, clerics and magic users who tend the garden need special eldritch defenses.
Typically, druids answer the call as frontline defenders, their magic is more subtle than magic users and clerics. However this is a general guideline, not the rule. The druids of Nace have developed a devastating area of effect spell, which does not damage the garden. They do not know the term "upward leader lightning", but they do know how to make lightning jump from the ground, through a target and into the sky. They call this Arclight.
Arclight
Level: 6 Components: V, S, M
Range: 0 Casting time: 2 segments
Duration: Instant Saving Throw: Special
Area of Effect: 10 yards
Arclight is a powerful spell which will cause a lightning stroke to leap from the ground below a target and into the sky. This spell is an area effect spell which is targeted on the ground below the target and does not move with the target. The spell has two damaging mechanisms, both allows a saving throw.
In the first segment of casting, a powerful electric charge forms below the target. They will sense this by the heating of their body, a corona around metal objects and a crackling sound. All creatures in the area of effect are entitled to a save vs spells. If successful, the target(s) flings themselves out of the target area taking 1d3 points of damage. They are stunned for one round and are prone. If unsuccessful, the target freezes taking no damage.
In the second segment of casting, the lightning discharges. Victims in the area of effect take 6d6 points of damage. A second saving throw halves the damage. If the victim doesn't die, they are stunned for 1d6 rounds.
If a person in the target area is flying, they can escape with no damage if they make the first saving throw. If they are forced to make the second saving throw, they will also fall out of the sky due to being stunned. This is typically a graceful wallowing, not a plunge and inflicts no more damage.
Levitation provides no protection from this spell, in fact, it will disallow ALL saving throws, period.
If a target normally or magically has the ability to leap, bound or stride great distances, they are entitled to a +2 to each save. This is normally limited to haste and jump spells, boots of striding and leaping or other items available in your campaign setting.
Since the boundary of the area is not visible, mechanically speaking, someone sprinting will be unlikely to be in the area of effect, unless they are incredibly unlucky. It is very difficult to target a runner, but it is possible to cast at an empty area and hope someone will run into it. This requires great timing, there is no roll for this. The DM should give the target the benefit of the doubt, either adding a good bonus to a save or declaring that they crossed the area too fast to be caught in the spell. It is possible to measure out the movement, but really is too complex for fast play. It could be described for dramatic purposes.
If a person standing on the edge of the area attempts to push someone back into the area they are escaping, contact with the victim will cause them to suffer the same fate as the person pushed. They are not entitled to any saving throw, they take the exact same damage as the victim. This is the price of being a jerk.
This spell does not damage non-living things, however it will damage undead. It does not cause flammable items to burst into flames, unless the DM rules that it does.
Additionally, if the caster attempts put themselves in the area of effect, the caster receive no saving throws at all and the damage will be a full and flat 36 points.