[Sw1] Crescent Moon Sword
This skill is amazing for damage in stage and PvP. Sieg winds up and swings his sword, releasing a wave that damages enemies up to 4 times and pushes them back with the wave. In stage, this skill can be spammed anywhere for high damage. In PvP, this skill can be used to easily deal damage equivalent to 10-20% of an enemy's HP, and thanks to the new patch, it can be dash cancelled and comboed after. However, this skill is quite costly in MP, and shouldn't be randomly used or else you could end up short on MP, and in a dangerous situation. This skill is very good to use after Whirlwind Wave since you can cancel decay and use this for its full damage.
PvP: 0 or Max
[Sw2] Hurricane Sword
A useful skill in stage and PvP. Sieg drives his sword into the ground and a small missile comes shooting out of it, hitting anything touching it. This skill can help with pushing mobs back and also for the air multiplier. In PvP it is good for mindgames and can also be followed by Destruction Fist if used correctly. In stage the uses are basically limited to hitting stuff on the ground and pushing stuff back. The damage isn't very good so it is best used for combo purposes. Stuff not hit at point blank may not be carried. Enemies in the air can be carried depending on height and position. Enemies standing in the path of the missile will be knocked down.
Stage: 0 or 1
PvP: 0 or 1
[Sw3] Thunder Sound
Originally Posted by Skiegh
I see very few Siegs ever make use of it but Hurricane Sword can be followed up by >>A if it hits more than once. As such, it can be used as a reset much like Sky Slashing only much more tricky.
This skill is a bit different than the others in the sword section. This skill is non-elemental, so it can critical from Sieg's skills. Also, this skill can slow down the enemies wihin it's range. Sieg raises his sword and drives it into the ground, causing a large shockwave that knocks down nearby enemies and slows them down according to skill level for 10 seconds. The slowdown affects all enemies within the range no matter the height the enemy is at. Enemies close to the ground in the air lose air time and have a minor position change. This skill can be cancelled at anytime by dashing. Stage uses are knocking down enemies for an escape route. PvP uses are knockdowns, cancels and slowdowns. The damage of Thunder Sound is horrible so it's not worth getting it for damage.
Stage: 0 or 1
PvP: 0, 1 or 9
[Sw4] Whirling Sword
This skill is very useful for Siegs in stage and in PvP. Sieg throws his sword forwards, dealing 3 strikes to the opponent with the spinning sword, knocking the enemy into the air with his 3rd strike and his sword returns to his hand like a boomerang. If you are hit when/after the sword leaves your hand, the skill still activates and the enemies in the range will be hit although the animation isn't shown. Enemies standing right next/behind you will be hit once, enemies close to you in front will be hit twice, enemies far away will be hit once and enemies in the effective range will be hit all 3 times. In PvP, Whirling Sword can be used for high damage at beginning of combos, and can be cancelled by dashing to the sides or back, >>A+S or >>ASpace (It takes quite a bit of practice though) so you can continue with >>A, a skill or A. Also, this skill is good for knockdowns. In stage, this skill is useful for mildly large group of monsters and bosses. Since this skill is ranged, you can have a bit of distance from your opponent so you don't get smashed in the face as you're trying to use Whirling Sword. This is a must max skill for PvP, and is definitely worth considering for stage. With the new Sieg patch, a maxed Whirling Sword can do over 500 damage per hit in PvP and in stage, so this skill is now a definite must max.
[Sw5] Flash Fate
This skill is good for PvP, but I don't think it will work as well for stage. Sieg swings his sword 3 times, and launches 3 waves that explode upon contact. Since the new patch allowed Flash Fate to be forward dash cancellable, this skill is now much versatile in PvP and in stage. This skill is extremely good in 1v1, since it doesn't pierce enemies, but it does explode, which can also damage monsters very close to the exploding area. However, if the enemy is too close upon initial casting, it might only deal 2 hits, and the 3rd one ends up missing. If the enemy is touching you from behind (God that sounds weird), then they may take a hit before dropping to the ground. Strangely, if the opponent is offcentered, it might land all 3 hits even if they're too close to you. In PvP, this skill is best used after Blow or Whirlwind Wave since you basically have a free shot (Provided you know how to time the skill after Whirlwind Wave, and you use fast enough after Blow) with Flash Fate. In stage, this skill isn't as good since you cannot move while casting this skill, and if a boss like Lunia uses an OHKO AoE attack, you're basically wearing a sign saying "HIT ME!" However, the long range of this skill allows you distance from the mob/opponent and you'll be safe unless the mob/enemy is charging you at 50 k/h. Also, this skill shouldn't be randomly spammed in PvP since it's a simple matter to approach and bash your head in with a high damage attack (Fury of Land, Destruction Fist, Rhapsody of Blood, Lightning Arrow etc). The new patch now allows Flash Fate to do 500+ damage per hit, so it is a good place to invest if you have the points.
Stage: 0 or 1
PvP: 0, 1 or Max
[Sw6] Whirlwind Wave
A must get skill for Sieg. Sieg swings his sword, and 2 or 3 tornadoes appear and chase your enemies. This skill is extremely useful for Sieg because it basically allows you to get a free hit on anyone with any skill if they get launched, puts pressure on opponents when it's chasing them, reset your damage decay and continue combos with large amounts of air time. On unjuggleable monsters, this attack keeps damaging them. If the boss/monster dies, then the tornadoes targeting it will continue in a straight line that damages anything in its path. In PvP, if the opponent respawns and the tornadoes haven't run out yet, then they will follow the opponent again when they reappear.
PvP: 2 or 4 depending on preference.
[Sw7] New Whirlwind Wave
Same thing as whirlwind wave, except this skill makes a LARGE tornado. It moves forwards at a slow pace and launches enemies higher than nado. Any skill can be landed after this skill if the timing is correct, but since the enemy can't be seen, it is harder to time than the normal whirlwind wave. It is pretty useful as a shield in stage since you can hide in the tornado. This skill as a set range and will not go up like the normal whirlwind wave.
Requirement for this skill is to be rebirthed at least once.
Stage: 0, 1 or Max
PvP: 0 or 1 for looks