They're really fun to write. It's an enjoyable challenge to write Xellos/Filia and make it believable without actually compromising his Mazokuity. I do love the pairing but I've seen too many fics where he's a sentimental sap and it makes me cringe. :D;; That's not Xellos. D:
(Although, what he's referring to - that scene in TRY where he threatened to kill her in front of Saichuro? His body language and how he held his staff was identical to when he takes a defensive posture waiting for an oncoming attack, rather than when he's intending to take the offensive. Doing that would also put Filia within his immediate ability to shield without making it obvious to anyone what he was doing, and Filia's expression throughout, she shot him a look that was more "...the hell is wrong with you?" there, and the true look of fear was directed at Saichuro. Xellos doesn't make idle threats, yet Saichuro didn't do what Xellos demanded, and he didn't kill Filia - he shoved her back behind him and wenet for Saichuro himself -- after the old dragon admitted the truth of what really happened to Filia. Yes, I've analyzed that scene too much. XD