Dueling 101: SEGOC

So what is this SEGOC crap? you ask. Since Konami fails to explain it on their rule book (causing most people to not know this). I shall explain it here.

SEGOC stands for Simultaneous Effects Go On Chain

SEGOC will occur when multiple Spell Speed 1 trigger effects trigger at the same time.


e.g. Two mystic tomatoes suicide in to each other. Both are destroyed by battle and sent to the grave at the same time, hence their effects trigger at the same time.

In this case, SEGOC will kick in.

Before we talk about SEGOC, let talk a bit about mandatory and optional effects

Mandatory: Effects that must happen no matter what, unless it is impossible to perform the effect.
e.g. Sangan: When this card is sent from the field to the Graveyard: Add 1 monster with 1500 or less ATK from your Deck to your hand.
Note there isn't a 'you can...' clause so this must happen unless you have no monsters with 1500 atk or less in your deck. In that case you must show your opponent your deck to prove you don't have a viable monster.

Optional: Like the effect name, this effect is 'Optional'
e.g. Dimensional Alchemist: When this card is destroyed and sent from your side of the field to your Graveyard, you can select 1 of your banished monsters and return it to your hand.
or
Watapon: If this card is added to your hand from your Deck by the effect of a Spell, Trap or Monster Card, you can Special Summon this card on your side of the field.

Optional trigger effects can not be activated if there are no viable targets.

There are two kinds of optional trigger effects, the 'when..... you can....' and 'if.... you can...' These will be covered in another dueling 101 topic. For now just regard them as Optional Trigger effects.

Back to SEGOC
The rules of SEGOC follows:

The Turn Player (which ever player the current turn is) Mandatory effects will be placed on the lowest chain link starting from chain link 1. If there are multiple mandatory effects, the turn player chooses which order they go.

The Non Turn player Mandatory effects. Similar to the Turn player, but this time it's the opponent's turn.

The Turn Player Optional effects. Same as the mandatory effects, but it is optional effects instead.

The Non Turn Player Optional effects. Same as above.


Right Now let's go through some examples:

Player A controls Dandylion
Player B controls Sangan
Player A uses Dark Hole
Neither player respond to dark hole, both monsters are destroyed.

Now apply SEGOC, since player A is the turn player, dandylion will be placed on chain link 1 while the non turn player's sangan will be placed on chain link 2.
Then the chain resolves backwards. So player B searches with sangan and then player A summons 2 tokens from dandy.


A popular question of mine:
Player A controls AOJ catastor
Player B summons Neo Spacian Grand Mole
Player B attacks with mole

Apply SEGOC
Both catastor and mole triggers at the start of the damage step. But mole has an optional effect while catastor has a mandatory effect. So catastor will be placed on the chain first no matter whos turn it is. So mole will always resolve before catastor and return both monsters to hand. After that, since mole isn't on the field anymore, catastor can not destroy it.


Right that's examples over.
Now I need to talk about some confusion with SEGOC.
SEGOC will only occur when the trigger effects trigger at the same time.
Tributing sanga for caius does not start SEGOC. Sanga must be sent to the grave first before caius hit the field, so sangan triggers first. Then caius kicks in and triggers it's effect. But this gets a bit complicated which I will discuss in the next lesson.

Also, SEGOC effects are always put on a new chain, they will never chain to an already resolving chain.

That's all for now, you can try some of the questions if you want. Ask me any queries if you don't understand.


Questions:
Player A controls: Machina peacekeeper, Sangan
Player B controls: Light pulsar dragon
Player B uses dark hole

Player A controls: sangan,dandylion
Player B controls: Sangan
Player B summons treeborn and player A activates torrential tribute

Player A controls: mystic tomato (in atk mode)
Player B controls: mystic tomato (in atk mode)
Player B uses tomato to atk player A's tomato

Turn player's DCK and LADD, and non-turn player's DCK simultaneously chain (according to SEGOC rule) to Gale's effect. Since all are mandatory, Turn player decides his DCK and LADD chain order and then, the non-turn player DCK becomes chain link 4. Upon activation, both DCKs are tributed to fulfill their cost. Upon resolution, only the chain link adjacent to the triggering event (Gale's effect) will resolve properly, and the others will resolve without effect. The best decision Turn player can take would be to chain link 2 DCK and chain link 3 LADD, as LADD decreases its stats at resolution. Otherwise he'd have a 2300/1900 LADD in the end. As for Gale's effect, assuming it targeted his opponent's DCK, it would resolve without effect since it lost it's target.

SEGOC is so much fun!

Let us continue the game. My turn: I draw.

I'm serious here. I draw a Wind-Up Shark.

I activate Wind-Up Factory. I use my Wind-Up Zenmaighty's effect to special summon Wind-Up Magician from my deck.

How do I get the most out of this play and by what exact mechanism? (involves SEGOC)

Warning: this one is very tricky to get right.
Hint: TCG rules differ from OCG ones.

Note: IIRC tributing Sangan for Caius generates a SEGOC situation, and it also goes differently for TCG and OCG.