...but no, seriously
If you have too many elements, it'll just get confusing (see above). It doesn't matter how careful you are thinking it through... some of the relationships will be ambiguous. In your six-element system, both the inner trio and their relationship with the outer trio make no sense to me. It's obvious that "Light" is going to be good against "Dark", or possibly vice-versa, but how is "Void" different from "Dark"? Why do plants beat electricity? Wouldn't space kill plants?
As MadWatch says, a good way out of this quagmire is to break out of the one-dimensional rock-paper-scissors approach and work with multiple
differentiating factors. For example, Disgaea has 6 ways to do well in attacks and 5 ways to do well defending, and different units are good in different ways.
(Attacking: high ATK for more damage, high range, high HIT (allows criticals, stops dodging), fast movement (allows flanking for more damage), Special Points (allows special attacks), high INT (more damage with magic spells).
Defending: high DEF for raw defence, high SPD to dodge, fast movement to run away, high RES to resist magical attacks/special attacks, high "Counter" to allow damaging counter attacks when attacked.)
The Starcraft series has multiple overlapping simple systems which allow for a wide range of unit types that interact in complex but largely intuitive ways. As a rough primer:
- A unit can be a ground unit or a flying unit. Air units can bypass terrain to gain advantages and can see up cliffs. On the flipside, many units' attacks only work against air, or only work against ground.
- A unit can be "Light", "Armored" or "Massive". Other units can have damage bonuses against certain classes. "Massive" units are immune to some abilities.
- Different units have more or less health for their cost. Conversely, different units do more or less damage over time for their cost.
- A unit has an armour value which is subtracted from attacks. High armour is effective against many small attacks, but makes little difference against few powerful attacks. Likewise, a unit can either attack rapidly but weakly, or it can attack powerfully but slowly.
- Units have movement speeds. A faster unit can run away from a slower unit. (Several units have 'snare' type abilities which prevent fast opponents from running away.)
- Units' attacks have ranges. A unit with higher range is able to get free hits on a unit with shorter range; if it's faster as well, then it can attack with impunity.
- Some unit attacks have splash damage, which is effective when fighting multiple small opponents but not when fighting single opponents or large opponents.
- Some units have shields and energy, which in turn make them vulnerable to special abilities which target shields and energy.
- Some units can cloak, which makes them immune to enemy units unless detected by one of a handful of specialist detector units.
- Some units can carry other units, temporarily making them highly mobile but weak and vulnerable.
- Units are classed as "Biological" or "Mechanical", making them vulnerable to certain abilities.
On top of all that, almost every single unit has a unique ability which interferes with the above mechanics in an interesting way.
The system as a whole seems complex... but in any given encounter between two unit types one or two of these factors will dominate, allowing one side to prevail for an intuitively obvious reason.
To bring this back to your system: consider allowing enemies to be "Physical" or "Ice" or "Fire" and
"Light" or "Dark" and
, say, "Fast" or "Tough" - where, say:
- Physical is strong against Water, which is strong against Fire, which is strong against Physical
- Physical is weak against Fire, which is weak against Water, which is weak against Physical
- Light is strong against Dark, Dark is strong against Light
- Light is weak against Light, Dark is weak against Dark
- Fast is strong against Fast, Tough is strong against Tough
- Fast is weak against Tough, Tough is weak against Fast
A particular enemy might be "Physical" and "Fast", meaning fire attacks and fast attacks are good against it, but tough attacks tend to miss... unless you use a spell or trap to stop the enemy moving around, temporarily stopping it from being Fast.
Another enemy might be "Dark" and "Fire", meaning Light attacks and Ice attacks are extra powerful but Dark and Physical attacks are weak.
A third enemy might simply be "Ice", meaning that physical attacks are strong, fire attacks are weak, but everything else is largely balanced.
Under a system like this, enemies would have one or more attributes. Your attacks, also, would have one or more attributes. You would have spells to counter certain attributes, eg. traps/snares to use against Fast enemies; dissolve spells to use against Tough enemies to weaken their resistance; a spell that combines *another* spell with a sword attack to make it Physical, or a "blessing" card that makes your next attack Light; a potion that makes you faster, so you can't be hit by a slow, tough enemy; a temporary shield, which fends off fast attacks but breaks against tough attacks...
The benefit of a system like this is that each dimension is simple and comprehensible by itself, but you can easily combine them in interesting ways to create a great range of different abilities and situations.