You can't, for two main reasons.
1. You can't summon Black Phantoms into your world. The only time you have even a tiny bit of control over when a black phantom invades your world will be right before the Final Boss in the Tower of Latria, where either a computer generated phantom, if offline, or a human opponent of roughly your level, if online, will appear. Every other black phantom that appears will be hostile towards you, so unless you sneak up on them soulsucker isn't very likely to work.
2. You can't really choose who invades your world. Black phantoms invade worlds at random, with the only control variable being their soul level in relation to yours: if the two are close he can invade you, if they are not close he can not and will invade someone else. So at any time anyone could invade your world, while you are in body form of course, and more likely than not they will be out to murder you and steal your body so soulsucker probably won't work then either.
Blazingdragoon4 - 7 years ago
You can summon a phantom to duel, but it's rather rare to find a Duel stone (it's like a stone to summon a Blue Phantom, only red).
If you have the stone you could always message someone who has been a Blue Phantom for you or any other player you've met but for them to trust you would require a lot of patience and mostly you would have to be soul sucked first for them to really trust you.
It's kind of a high-risk, high-reward situation.
Solipsistico - 6 years ago
Try soul sucking red phantoms. I recommend going on the forums and trying to find someone who wants to increase their soul level.
NColdhardt - 5 years ago
This question was asked more than 60 days ago with no accepted answer.