I think it's flavor goes both ways actually. When the Trader moves into a conflict he is bringing your army supplies in the form of fate or conflict cards he has earned during his time trading. When a character you control moves into the conflict he shares the supplies/resources he has acquired with them.
What I thought added to this flavor was the fact that you do not need to own the character that moves into the conflict in order to trigger the Trader's reaction. Even when your enemy moves to oppose you, our favorite Ide doesn't let that get in the way of his job and finds a way to acquire resources for the Unicorn. Love it!
Edited by Shinjo Sousuke