Only complete isolation of the mind from all interference would defend against it, cause it a conceptual thing it does, cause SoE is the temptation to preform evil all people have at some level, so without literally lobotomizing yourself it would be able to get in.
I believe Archive Hunter is the only human that actually defenses against the invasion. Cause his mind is basically like no ins or outs, complete lock-down. And even then that is not really defending against it, more accurate would be calling Archive Hunter an invalid target for this ability.
Granted Forest would be difficult for SoE to fuck with in her own way, with her being really fucking old and probably having a really stable mind. Forest would probably be one of those gradual jobs that SoE likes so much. Granted events that occur can be used to accelerate the process, even momentary lapses or depression acting as a suitable foothold cause he will make a 'mountain of of a molehill' to start eating at her.
Tom I am not even to sure if it would work at all because of what he is, would have to work that out with Alice.
I think this is a bit too much, considering that you want us to RP SoE.
Then ill tone it down a bit. But really he would never do this.
Cause that is basicly forcing someone to do something, and he HATES that. He wants to them chose evil on their own with just a slight nudge.
Edit: Ok Ivan, I made it so they just suffer pain with the effect fading quickly as long as it is not extended contact. Also a note how he hates using it. Hope it is more reasonable.