Also, did you ever bother and try finding all the lens? I'm guessing you'd get some pretty sweet rewards for doing so.
Yeah. XD I rarely try to link them anyway. Mostly I'd just go Rising > Burning Phoenix.
Omega Seal,last move, yes. When both Slahs and Thrust are at L30. On its own, Omega Seal is useless (except perhaps for the stun part. XD). But while the enemy is 'floating' in the air, just before Reid slashes downwards, press the Omega Seal button again. (To avoid missing it, just repeatedly press it, like how you'd try to extend Burning Phoenix XD). It'll extend to Quasi Seal, a one-hit KO move (deals around 20,000 HP) But you have to first satisfy these conditions:
1. Omega Seal has been used at least 50 times.
2. There is only one enemy on the battlefield. (i.e the last enemy)
3. The enemy can be lifted into the air (i.e this technique does not work on heavy/floating enemies)
4. The enemy has less than 20,000 HP.
5. The enemy has a Wind resistance of less than 50% (ergo, could almost never be used on bosses, except Valkyrie.)
Watch this. The third technique used is Omega > Quasi Seal. There used to be one video complete with all skills, summons and Maxwell Extension, but I can't find it now. The one I linked to was okay, but it doesn't have all the summons and team skills extension, and the audio is somewhat... cheesy. :x On the up side, the background music is Garnet Crow's Flying so there's a plus there
Lens, yeah. Because I kinda followed the walkthrough step by step. XD Otherwise, it'll be REALLY hard to find those lenses. x.x
The rewards are Combo Command, Inferi Cape, Celesti Cape, Extreme, Krona Symbol and... a title. lol. I always fail to execute commands properly using Combo Command, so I don't really use it that much.
The capes are nice depending on what enemies you're fighting. (E.g Equipping Reid with a Square Shield, a Flare Cape and an Inferi Cape makes him almost invincible to the fire attacks from the tournaments, each dealing like 1HP of damage; can also be used on Meredy in case you want to have Maelstrom on her. But Waterclouds are better anyway.)
Extreme can only be equipped on some characters; what it does is that it raises a tremendous amount for attack (+300) but lowers Defense and Evade (-200 and -20 respectively). I never used it.
Krona Symbol protects you from all ailments... which isn't really needed because you can simply used the Panacea Bottles or Support Artes to protect the whole team. (Unless, of course, if you get this thing at the BEGINNING of the game, then it'd help a lot. XD) But it is extremely useful if you want to go level-grinding. Equip the character that you want to level up with Krona Symbol and Demon's Seal. Demon's Seal doubles the experience a character gets, but inflicts status ailments on that character. Since Krona Symbol neutralizes that, you can continue bashing enemies without having to worry about being Poisoned or whatever.
And the title is for... bragging rights. lol. And completion purpose.
From all those 3 extensions, which one you like best? XD
And, have you tried out Maxwell's Extension?
...Wall of text. XD