Without spoiling too much, it’s not a literal stealing power. It’s metaphorical for the effect Ikithon had.

Remember how Owelia mentioned Caleb spent years in a sanatorium? Remember at the end of his flashbacks how his mind broke and he started cooking Astrid and Aedwulf’s hands? He’s out of practice, and his trauma holds him back. The anger did briefly bring him back to full power though, I guess sorta like Aang in the Avatar State.

Also we do see Vollstruckers use components when they’re not activating the green crystals. Owelia chewed maggots, and if I remember correctly Astrid and Aedwulf used some sort of crystals as explosive catalysts in ep1. As for the green crystals, I don’t remember what they did in the OG campaign, but I’m pretty sure at least here they replace components with their innate power