I have been writing a detailed guide for Shadow Sabres which is available here:
https://batmudnotes.blogspot.com/2022/08/shadow-sabres-notes.html

That being said, I wanted to give a quick overview of Sabre Fencing for new
members. Many chessboard pawns have died to bring us this information

Mechanics:
- Sabre Fence will let you specify three different "fencing" skills
that it will cycle through after you execute the sabre fence skill.
- You can use Sabre Fence on its own, without any additional skills, but it
underperforms. This means until Level 15 in the guild you are better off using
Gloveknock as your main attack.
- When using Sabre Fence with fencing skills, you can start to use other
skills/spells while it is active. Therefore, the highest damage skill usage
after 15 levels in the guild is 1) Sabre Fence, 2) Gloveknock, 3) SabreFence,
repeat
- The Sabre equipment "feather" quality helps prevent your follow-up
spells from being interrupted. This is important if you are dual-classed as a
mage-like guild
- The Sabre equipment "hat" quality helps prevent your follow-up
skills from being interrupted. This makes it useful if Sabres are your primary
guild.
- Sabre fencing techniques are broken into "Offensive" skills and
"Defensive" skills.
- The word "Defensive" is misleading. They are more utilitarian
skills. All Defensive skills will increase the damage of the next offensive
skill significantly which is the main reason to use them in you fencing
combos.
- Combo skills may have a secondary action/attack/impact that triggers if they
are in the 2nd or 3rd spot of your combo. The secondary action will never
trigger for the first technique in your combo
- Therefore, you are usually best off having an offensive technique, defensive
technique, offensive technique as your combos. The defensive technique in the
middle is nice since the enhanced damage to the following technique is
significant.

Offensive Fencing Skills: The following fencing skills are offensive in that
they directly cause damage to your target.
- Sabre lunge
-- The secondary effect is it will do an extra "hit/damage" if you
score a critical hit while it is active
- Sabre remise
-- The secondary effect is it will do an extra "hit/damage"
occasionally if you miss an attack.
- Sabre trompement
-- I still haven't found a secondary effect for this. Right now it seems worse
in every way to the other offensive techniques.
-- Even the damage doesn't seem to be more. No idea why this is useful. If you
have any information on this please share!
- Sabre riposte
-- I still haven't found a secondary effect for this. Right now it seems worse
in every way to the other offensive techniques.
- <<Have not advanced enough to test out Sabre Tension Parry>>

Support/Defensive Fencing Skills: The following fencing skills are
support/defensive in that they try and prevent the attacker from causing you
damage and they enhance your other attacks
- Sabre parry
-- The secondary effect is you will sometimes parry one or two attacks from the
primary target you are using this against. Pretty nice defensive buff
actually.
- Sabre feint
-- The secondary effect is you will sometimes do a bonus hit/damage with this
technique. Not as good as an Offensive technique, so the main reason to use
this is the damage buff it gives. Still, any damage is good damage!
- Sabre derobement
-- The secondary effect is you will sometimes do a bonus hit/damage with this
technique. Seems similar to Sabre feint. Not sure why you would use this vs.
Feint
- Sabre invito
-- No idea what the secondary effect of this skill is. If you have figured it
out let me know!

Recommended Skill Combos:
- For people with 15-20 levels in Sabres:
-- Sabre lunge, Sabre parry, Sabre remise
- For people with 20-25 levels in Sabres:
-- Sabre lunge, Sabre parry, Sabre remise
Not a typo. In my testing I really haven't seen value in switching to more
advanced fencing techniques yet, so this is my current setup.
You can also do (Sabre lunge, Sabre remise, Sabre trompement) if you are
killing smaller creatures and your 3rd technique doesn't have time to fire
consistently.

General Disclaimer:
- This is based on my own personal experiences. I can totally be wrong. If
anyone has corrections, insights, or suggestions please post a follow up, I'd
love to learn from you.
- I'm really bummed that advanced fencing techniques seem to be worse than the
basic ones. I feel like I must be missing something.