Important to know is. before level 50 you need much Physical defence but from level 50 of the catacombs come only the big eye as boss.
The boss make only magic damage. So you just need a lot of magic defense and a lot of hit points for your Argoran Shield.

Skillusing from the Boss:
First thing you need to know and learn about the level 50+ eyeballs what skills they use and in what order.
the boss use first 1 lightning bolt, then use he his AOE magic ability. This has a chance to stun for 1 turn.
After this he use again 2 lighning bolts and then the De-Buff. The key to the debuff is the number of turns it's in effect, 3.
After he casts his debuff he casts one lightning bolt, then casts his eyeball roll (which also applies a slow).
After which he starts the cycle over again with 2 lightning bolts.

Your tactic:
Well first off, you need to have your double attack timing.
When he casts his eyeball debuff, the -def and attack, you need to double attack for two turns.
The execution of this is exactly the same as world boss.
You need to anticipate the timing of this, so you can start your double attacks the turn he casts.

Skillung What you need:
With this Skillung you can Beat the Complete catacombs.
but you need Minimum 8000 MDEF and 8000+ PATK good thing is 25-28k HP for Argoran Shield
with higher level finish first the defence skills

My Current Academy Setup:
this picture is from my mage sry i dont have a knight

Make a Focus on your Hero PATK after that come Hero MDEF then Hero HP.
the rest ist Optional and no need for Catacomb Except Troop PATK when u have PATK Enlightenment

Your Troops:
The Best troops in the catacomb are Angels my Angels are atm level 52
but with lv46 Troops you can Finish the complete catacomb.
Take your troops ever behind you Because The boss hit first everytimes the rear
so you become not damage. only the D-Buff and the AE hit you in front.

Now we go to the stats of your Equip:
Knights are the best stats for Physical Attack, Block, defense, hit points, magic defense.
The first four are a must have when you get to the other, it is Cool.

Now we come to the socket's:
The First socket Physical Attack if you have more, second as HP, the third Magical Defense, and with epic in the fourth socket Physical Def.

Now we come to the Astral's:
this three Astrals are a must have:
Astral first you need is Force. The more level the better the Astral.
Second Astral should be willpower. The more level the better the Astral.
Third Astral should be enhanced Illusion. Minimum level 4
and these Three Astrals are Optional:
(you can take two from them what you want)
Fourth Astral should be enhanced Will Destroyer. The more level the better the Astral.
Fifth Astral should be enhanced ruthlessness. Minimum level 3 but higher is better.
Sixth Astral should be Pristine Enshieldment. The more level the better the Astral.

The fight itself is very simple:
1) Start the battle with Shadow Thrasher.(you need 35 rage on every boss)
2) then use Slasher and safe your Rage for Argoran Shield and Shadow Thrasher.
3) Argoran Shield use only after the AE from the boss.
4) try to Expand your bleeding with Shadow Thrasher.

That was the whole fight. you just need these three skills no other skills.
With level 50 and these stats and Astral from this guide You can beat Easy level 100 catacomb.