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Quoz
2018-01-20, 02:35 PM
I recently finished GMing a lengthy game of Force and Destiny in Star Wars. One of the aspects that I felt make the setting come alive was the mechanic for vergences, which could change how players could tap into the force at a given location. In some areas teeming with life, it was easier to access and gave more powerful results. In other places, like a dead planet or an abandoned Jedi prison block, could make it much harder to use at all. Still other locations could be highly attuned to a specific aspect, such as a temple that gave powerful visions of the past and future.

I would like to introduce something like this into D&D, but I think the spell-based magic would be harder to strike the right balance. I would love to run in a world where a bleed from the Feywild makes illusion more difficult to pierce, or a corrupted graveyard empowers necromancy and hinders healing. The effects should be real enough to have a tactical impact, but not so overwhelming that it would sideline characters who are not positioned to take advantage.

Some of the terrain based effects I am looking at now:

Give advantage or disadvantage on saving throws for one school of spells

Any spell cast counts as being cast at two levels higher

Healing effects that include rolling dice heal only the minimum amount

Any creature summoned gains a temporary buff (extra HP, higher AC or saves, ect)

When you use a spell slot to cast a spell, roll a d10. If the die is equal or lower than the spell level, it causes a wild magic surge as per sorcerer. If the caster is a wild magic sorcerer, instead roll d10-2.


Has anyone ever used a mechanic like this in D&D? What works, what doesn't, and what should I consider when setting up an encounter with terrain modifiers?

What kind of interesting effects would you want to see as a player or GM using this mechanic?

JackPhoenix
2018-01-20, 02:58 PM
Not in 5e, but 3.5 did this with planar traits, and for Eberron, with manifestation zones and the whole "planar orrery" model, where plane would influence the world when its "orbit" reaches its point closest to the world.

It shouldn't be that hard to create something similar in 5e, however, 5e doesn't run on small numerical buffs, and magic has less "tags" than in 3.5e, leading to less granuality in which spells are influenced by what.

Lombra
2018-01-20, 03:56 PM
Making it impossible to cast spells of level x or higher could be another nice trick, not being able to upcast too. Advantage and disadvantage to saving throws is pretty powerful so I'd use it moderately.

PhoenixPhyre
2018-01-20, 10:02 PM
One thing to consider is how you let the players know about these effects. Anything that comes across as "gotcha" or untelegraphed can be quite annoying.

I had a DM who pulled something like that--

We were approaching a temple inhabited by bad things (raven spirits, seemingly). We got into a fight, and I (playing a cleric) popped spirit guardians. He didn't tell me (or give me any warning) that I not only wouldn't be able to control who it targeted (which you normally can), but I wouldn't be able to end concentration on it normally. No "the place seems strange," no checks, nothing. Just a wasted spell slot (at 6th level, so that was one of two 3rd level slots) and some friendly-fire damage, as well as rendering me (due to the other effects) basically worthless that fight. Somehow I was somehow supposed to know that the place would hijack my spells without any warning. It was frustrating.

Quoz
2018-01-21, 01:11 AM
I definitely agree about no gotchas. The systems I have been running used dice pools instead of target numbers and modifiers so I couldn't really hide mechanics well anyway.

Even if I were to run in a more subtle setting where I wouldn't outright state the mechanical aspects of the terrain, I would give a lot of hints and foreshadowing, and several opportunities to find out roughly how magic works differently in that location before setting up a major fight.