Vaseraga is a bigbody archetype character. This means that he moves slow, attacks slow, has weak neutral, but can systematically destroy his opponent once he gets them into the corner.
Vaseraga spends most of his time trying to get in on his opponent and back them into the corner, which requires a lot of patience. You can't be impatient and be successful with this character. However, once you get your opponent to the corner, you have some of the strongest pressure in the game by using his advantageous moves and his command throw.
Midscreen, there isn't much you can do to pressure your opponent. You can tick j.L, c.L, or c.M into command throw, but if they stand block, command throw will usually whiff after anything other than a jump forward j.L that lands right in front of them. This is because they walk back a very small, possibly even unnoticeable distance which puts them outside of the command throw range, where they would get hit if they crouch blocked due to staying stationary. This means that your ability to mix someone up midscreen consists largely of one tick normal into either command throw (to catch crouch blocking opponents) or 2M (to catch stand blocking opponents.)
The other option you have midscreen that doesn't end your turn is to space 6L from a far enough distance that it is plus on block. This is usually done off of an absolute max range f.M, or from a f.H. Otherwise, your options are mainly just a normal string into either 214L (to have a frame advantage while transitioning back to neutral) or 214M (to prevent them from pressing buttons if they may interrupt the 214L.)
In the corner Vaseraga becomes one of the scariest characters in the game. 214L is plus on block at most ranges and that combined with the long reach on his normals lets him pressure his opponents in the corner while being outside of his opponent's comfort range. Additionally, Vaseraga has a strong mixup game by ticking into his command throw in the corner with j.L, c.L, or c.M. If the opponent tries to jump out of this range where Vaseraga has control, he can convert an antiair into big damage and a hard knockdown.
Vaseraga is an extremely snowbally character, relying heavily on maintaining pressure after knocking down the opponent. 6x lets Vaseraga maintain this pressure from seemingly impossible ranges, throwing the opponent halfscreen while allowing him to get a meaty. Vaseraga's more powerful okizeme are as follows:
c.M is a whopping +4 on block, making it one of Vas's most deadly oki options. This little punch is larger than it looks, links into itself on block for a frame trap or on hit for a combo, and, if timed properly, can bait reversals. It also catches jump out attempts, so be ready to convert if you manage to hit an opponent that just left the ground.
c.L is +5 on block, being far more plus than other c.Ls. This can be used just as c.M is, but makes baiting reversals much easier since it recovers faster. c.L can be linked into 2M on hit, leading to a good amount of damage midscreen as well as high damage in the corner.
Great Scythe Grynoth
This is Vaseraga's riskiest oki option while giving him the least reward. Reserved for those that constantly respect your oki, this command throw throws your opponent fullscreen, where Vaseraga cannot run oki, even with a well-timed 6M. The reward in the corner is far greater, allowing Vaseraga to get Soul Forge up AND get a meaty. Be very wary of your spacing when using this tool, as its range is pitiful, only hitting foes who are directly in front of the 7 foot draph.
M Savage Rampage
This is an enormous gimmick that should be used lightly, but is worth noting. If you have a foe that likes to grab or DP on wakeup, using M Savage Rampage after knocking them down will handily bait their throw and most DPs, allowing for Vaseraga to get a delicious H followup counterhit, deleting their health bar. It's HIGHLY recommended that you only use this option if you already have Soul Forge up, as a stray hit from a larger DP may be your downfall. Some DPs, such as Percival's, will beat this option because it moves them further forward, hitting Vaseraga out of his armor.
Off of most knockdowns, Vaseraga can get a safejump j.L off. There's nothing too special about this safejump other than allowing Vaseraga to bait DPs if used properly, letting him get a fat punish as per usual.