For Nullification, you must make physical contact with the spell or ability you wish to nullify. You must place you hand directly onto the object or concentration of energy in question. For abilities like Optus's Stasis blessing and Lohkt's War Form blessing, you must place your hand onto the caster's skin.

For Evocation, you simply need the required amount of energy stored within yourself, you don't need physical contact with a substance source, you can create your own rock or fire, etc out of thin-air. However, having direct access to existing versions of the substance you wish to evocate will help. You can draw on the fire of a lit candle rather than use excess energy to create your own fire, but you'll still need to pour your own energy into the fire you draw from the candle, unless you intentionally want a tiny flame.

Detection is the easy one, you simply sense when disciples or other Marked are near by. And as you become more powerful, you'll be able to tell directions, distances, and in extreme cases, you'll be able to know just by looking at them.

The trade off for being able to do what you want with your power is the Curse of the Abandoned. Basically, all the gods are mad at you and want their disciples to take their wrath out on you. Some gods like Amlia might not wish harm or death upon you, but her disicple might be colder to you than to others, while disicples of gods like Urr or Lohkt might deliberately go out of their way to kill you. Giving you this negative treatment is considered a small part of every disciple's agenda.

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If anyone else wants/needs a deeper explanation of their powers, don't hesitate to ask.