I am working on a homebrew corruption system for my upcoming Diablo themed campaign. You can read more about the system in this chat thread. The complete system is too large and complex for the scope of this question so I will just summarise the relevant parts.
Corruption is gathered throughout the campaign by exposure to corrupting influences. The PCs have the option to either Resist or Embrace the influence when they encounter it. For each of these option there are three sub-options based on how they choose to resist or embrace.
These sub-options effectively form a skill tree that players can advance through as they gain influence. Each branch has 3 tiers of abilities. As the campaign is expected to run from level 1 to level 5. Players should be progressing in this skill tree approximately once per level. I.e. tier 1 abilities at 2nd level, tier 2 at 3rd level and tier 3 abilities at 4th level.
Below are listing the tier 1 abilities for each branch of the skill tree. The intent is for these to be balanced both individually and against each other. No option should be clearly better or clearly worse than the others.
Tier 1 resist abilities:
Delusion: You begin to dismiss things as illusions. You have advantage on saving throws against being frightened, but you gain vulnerability to psychic damage.
Defiance: You have found the inner strength to defy even the strongest foe. You have advantage on Strength saving throws, but have disadvantage on Charisma saving throws.
Radicalism: Others have begun to notice your Radicalism. You have advantage on Persuasion and Performance checks, but cannot be seen to back down from a fight. Your speed is halved when retreating from an enemy.
Tier Embrace abilities:
Temptation: Giving in has become so easy that it is almost second nature to you. You have disadvantage on Wisdom saving throws, but gain resistance to fire damage.
Darkness: Your blackened soul has begun to show. You have disadvantage on Persuasion and Performance checks. However, you also gain resistance to necrotic damage.
Hatred: Your sulking narcissist behaviour has clouded your judgement. You have disadvantage on Perception and Insight checks. However, you have advantage on saving throws against being charmed.
Players can only gain each ability once. However they will stack with the other tier 1 abilities. For example, if a character takes both Radicalism and Darkness abilities, the Advantage, and Disadvantage on Persuasion and Performance checks cancel out, leaving them with the speed deficit when retreating, and the resistance to necrotic damage.
I would like to know a couple of things:
Are these abilities balanced individually? I.e. Their bonus and penalty are roughly equivalent and giving them to a PC will not unbalance the game.
Are the abilities balanced against one another? I.e No ability is clearly better or worse than the others.