Under Night In-Birth/Offense and Defense
Blocking is very important, as it is in every fighting game. Hold back to block, or down + back to block while crouching. When you successfully block an attack, you will be unable to act for a short time. This is called blockstun. For the most part, you can only block while on the ground. While in the air, you can block projectiles, and you can use shield against other air attacks, but against most grounded moves you can't block at all! This means being in the air makes you extremely vulnerable.
Overhead and Low
Like in most fighting games, Under Night has overhead attacks and low attacks. Many attacks hit mid and can be blocked either standing or crouching, but overheads must be blocked standing, and lows must be blocked crouching. Most air attacks are overheads. Grounded overheads tend to be quite slow, but lows can be quite fast. Therefore, generally you should block low and look for overheads.
Shield is UNIST's special type of blocking. You can shield by pressing + , or + . Shield has several useful properties: It reduces blockstun by 3 frames on the ground, it increases pushback, and it gains 1 block of GRD. However, shield is risky: You can't switch quickly between standing and crouching shield, and if you get hit or thrown while attempting to shield, you will be GRD broken.
You can shield in the air to block your opponent's air attacks. This will reduce blockstun by 6 frames.
Green shield or Guard Shield is when you shield a move while already in blockstun(still reducing blockstun by 3 frames). Unlike normal shielding, you can switch between high and low block instantly. Green shield costs you 10 meter (or whatever is left in your guage if you have less than 10) and will also cost 1 block of GRD if the green shield fails to block anything.
Throws cannot be blocked. To perform a regular throw, press + . Regular throws have 4F startup. Throws can be avoided via a throw tech, also input with + . You can press this up to 14F after you're thrown. If you successfully tech a throw, you will gain 2 blocks of GRD, and your opponent will lose 2 blocks. Additionally, you will recover 8F sooner than your opponent.
You are invulnerable to throws during jump startup. What this means is, if you think your opponent will throw you, you can jump to avoid it. Lastly, you're throw invulnerable for 8F after getting up from a knockdown.
If you throw your opponent during blockstun, or up to 8F after blockstun or hitstun ends, it will be a gold throw. A few golden rings will radiate from the victim to show this, and the throw tech window is doubled to 28F.
There are times when throws cannot be teched. If a throw hits you during your move (basically counter hit, but for throws), then you cannot tech it, even if it's gold. If you have recently input a throw tech which failed, you will not be able to tech, even if the throw is gold. And finally, most command grabs (special moves that throw the opponent) cannot be teched, unless they're gold.
Throw option selects
Crouching Throw Tech
If the opponent attempts to throw you, you will tech the throw. If the opponent does nothing or tries to attack you, you will flash crouching shield briefly. This option select is used when there is too much risk involved with sticking an attack out.
This option select can be countered with a delayed throw or an overhead. The throw will then hit when the opponent's shield is flashing and GRD break them. An overhead will GRD break the opponent since it will hit during their crouch shield.
Crouching Jab Throw Tech
If the opponent attempts to throw you, you will tech the throw. If the opponent does nothing or tries to attack you, your chracter's 2A will come out if you aren't in blockstun. Otherwise, you will just block. This option select is used to beat opponents who are trying to run in to throw or are trying to delay their throw attempt.
This option select can be countered with a dash attack or a fast overhead (usually off of an assault). A dash attack will usually hit the opponent before their 2A can come out and result in a counter hit. An overhead will hit the opponent during their 2A animation.
Backdash Throw Tech
If the opponent attempts to throw you, you will throw tech. If the opponent tries to do nothing or attack you, you will backdash. This option select is used to beat opponents trying to break your throw tech attempts with assault overheads since the backdash will recover fast enough for you to block. This option select has limited utility in the corner for obvious reasons.
This option select can be countered with a very active attack or a slow attack. The idea is to hit the opponent during the vulnerable recovery of their backdash.
Veil Off/IWEX Throw Tech
If the opponent attempts to throw you, you will throw tech. If the opponent does nothing or tries to attack you, Veil Off will come out. If your character is on low life and has 200 meter, IWEX comes out. If you guess that your opponent is going to do anything except wait and block, this option select wins against every throw mixup.
This option select is countered by simply dash blocking or performing any other reversal baiting maneuver.
Guard Thrust is a universal defensive option that can let you escape your opponent's pressure. You can use it during blockstun by pressing 214 + . Your character will perform an attack that knocks the opponent away. If you are in Vorpal, performing a Guard Thrust will end Vorpal. If you are not in Vorpal, performing a Guard Thrust will cost 100 EXS and will GRD break you.