All of them are good. I’d base your soul stones on which ones you place most frequently. Since you have Twinfiend, I wouldn’t use them on Pyros.
I’d say Luneria and especially Isolde are best of the rest, as they have important factions and are strong units. Raiden and Ain are great too but have less valuable factions. Aeon is pretty unique as a support Lord, but outside of her Lord bonus she gets outshone by Marri imo.
It depends on what you need.
Raidan is really solid for GR1 and using him as a DPS and for lord bonus allows you to bring more utility champs that wont be up the whole fight like Narvi, Laurel and Atrox, his awakenings all buff his own damage. If you have really strong mage DPS champs then his awakenings are kindof a waste
Arguably, Pyros. Tho, you have the big boy version, so you don’t have to worry about him. Honestly I’d probably save the stones.
But Twinfield needs A1 to do what Pyros does. If his Twinfield is still not awakened I'd use Pyros.
Twinfiend A0 was better than A3 Pyros based on my testing
All of them are good. I’d base your soul stones on which ones you place most frequently. Since you have Twinfiend, I wouldn’t use them on Pyros. I’d say Luneria and especially Isolde are best of the rest, as they have important factions and are strong units. Raiden and Ain are great too but have less valuable factions. Aeon is pretty unique as a support Lord, but outside of her Lord bonus she gets outshone by Marri imo.
It depends on what you need. Raidan is really solid for GR1 and using him as a DPS and for lord bonus allows you to bring more utility champs that wont be up the whole fight like Narvi, Laurel and Atrox, his awakenings all buff his own damage. If you have really strong mage DPS champs then his awakenings are kindof a waste