I am not an expert, but if you combine Cloak of Resonance (new core) with Agnes Baker (old core), you get a pretty powerful combo:

1) Agnes takes an horror --> ennemy takes a damage

2) Move horror onto cloak of resonance using lucky charm --> ennemy takes another damage

On the next turn, you can even place this horror back to Agnes etc. which basically gives you a free damage each turn.

If you play with an investigator which has low sanity, you can even heal your ally... It seems very handy to me.