How come when Loki summons himself with Karen it uses her power?

Question

When Loki is one of Karens Spirits he summons himself to try to save Ares and while he's summoned Karren can't summon a second one because she's got his gate open. But later when Lucy has hi he summons himself all the time with his own power and he says it won't affect her energy stores like during the S-class trials he teams up with Gray but tells Lucy not to worry he won't weaken her any.

Answer 1

It's most likely that he used her power purposely to make sure she couldn't summon Ares. With Lucy he doesn't want to make her weaker so he uses his own power.