Technically, bane auras and modifiers are exactly the same.
The only reason there are 3 is to split the effects into 3 categories, and ass card with synergies to only one part, or cards that remove only some of them.
It's possible to do beneficial banes, or even modifiers that give armors rach turn, but I will just try to avoid it.
What I try to build:
- Aura: Beneficial effects usually attached to caster or its allies. Effects that activate at the end of turn (10 ward) and some reactive effects ("when fire damage is taken, do xx"), and resistance-type proactive effects (10 fire resistance).
- Bane: Negative effects attacned to enelies of the caster. Also effect at end of turn (5 magic), and vulnerability-type proactive effects (10 fire vulnerability)
- Modifiers: Effects either positive or negative, applied to any side. Contains all other proactive effects (+10 to damage done, +5 to ward gains, -20% to healing recieved...). Should never have effects that activate at the end of turn.
- Summons: Only activated effects, and usually one at random among several. The target can be different for every possibility of a single summon.
Edit: to clarify -
Proactive effects are effect applied just before another effect is resolved (incrementing / decreasing values)
Reactive effects are effects that trigger just after another one is resolved (can do anything in reaction)
