Order of precedence between rules

By Zut the Overlady, in Chaos Marauders


We had an issue about order of precedence between rules in one of our games. I draw a purple card that allowed me to discard another purple card into another player's line (sorry, I have only the French version of the game, so I don't know the cards' name in English). But, by placing this card in one of my battle lines, it completed this line.

The rules say that immediately when you complete a line, you may attack another player, but do I get to discard the other player's card before attacking? Do the text on the card takes precedence?

In many games I played, this is the case, but I'm confused about the word "immediately". What do you think?