based on Knights in the Nightmare, the WISP system, the game composes of Guardian Wisp where you obtain depending on the levels you go into (I'm thinking maybe how you interacted in Chapter 0 and 1 and a certain event will let you fight your first Guardian Wisp)
The wisp increases your stats and varies your abilities and as well as allows you to summon them via SP.
The system is the same as Valkyrie Profile/Atelier Iris/Mana Khemia. There's this "splash" effect from where depending on the positioning of the enemy you can hit all of them or depending on the level of the WISP spell it'll only affect 1 tile or something.
I was thinking of making items have skills as well like in Riviera/FF9 that for example,
Command Attack:
Einherjar - Slash - [EX-Overdrive]Disaresta (List effect)
Bronze Sword - Slash - [Overdrive Level 1] Double Slash (List effect)
I think that'll be a great variety so people can use strategy
The splash effect works here as well.
Items are usable too, although sometimes I wish I can add more variety to this than the usual lol items, maybe like in Diablo where items don't fully heal you instead it goes Regen-like. I think this should be fast-paced as well. I'm thinking of making weather contribute to your damage as well, such as if raining, if you use fire element, it'll weaken, if you use water element it'll get stronger, and there's this elemental relationship system like...
Wind strengthens fire
Wind strengthens water
water strengthens wind
fire weakens wind
Earth weakens water (vice versa)
Water weakens fire
fire weakens water
etc.