These two champions are gifted mages according to the lore.

One was encouraged to hone her talents.
Another's were shackled and sealed.

Would it not be natural for Syndra to develop animosity towards Lux?
Plus, it would enrich Syndra's lore, which is lacking right now, if this rivalry were to be introduced.

What do you guys think?

I don't think syndra would have any animosity towards her at all, don't get me wrong they wouldn't be the best of friends, but syndra would be a bit jealous of lux's upbringing. As for the fight syndra would win in the fight I think

in a straight up fight, i feel like syndra would win, but then again lux can hide in open sight, but then again syndra lives in a floating fort, but then again lux can charge her lazer, but then again syndra controls epic amounts of power, i actually have no clue

Syndra would pity Lux for the chains of servitude that were forced upon her but also loathe her for accepting them.

Now she's free of all restraints, I don't see what reason she'd have to be jealous of someone like Lux.

Honestly I'm kind of curious about how a fight between Nasus, and hecraim would go. Could nasus eat hecraims soul or Wither Hecraims body away or Would Hecraim just be to much for Nasus.

Syndra probably has more "raw" power than Lux, though Lux has more control/techniques. I believe that Syndra would be interested in Lux's reverse engineering ability, and encourage her to rebel against Demacia.

I feel syndra would be jealous only because Lux was not only allowed, but encouraged to let her power flourish and grow into more, while Syndra didn't get her full power until around the time she joined the leauge. Also syndra would probably have a thing for Xerath only because of his raw power, and almost unrivaled energy.

Next thing we know Lux is using 'light balls' to fight enemies. Spell steal go!

I think that Syndra feels that Lux isn't a threat and is far weaker than her. Afterall, Syndra allows her magic to be used freely as if it were water. Lux is a bit more controlled, something that Syndra would likely scoff.

On the flipside, Lux wouldn't underestimate her boasts. Syndra is a powerful mage by all standards. If Lux and Syndra did fight, chances are she would lose. At least the first time.

After that, Syndra's full power approach won't be as effective because Lux would have already learned how to counter it, or even emulate it herself to a lesser degree. If there is one thing Syndra lacks, it's adaptability. Lux seems to be a bit of a master at adapting to the powers of other mages, or even using their own abilities against them, as in the case of Morganna. If Lux isn't finished off in the first fight outside the League, I have full confidence in her abilities to defeat Syndra should their paths cross again.