Note: You do not need to guard against some of these, but you do need to predict them coming.
If you have his aggro:

1. Move to the side.
2. He will spin his beating stick backwards.
3. Guard that and after 1 second guard again.
4. Repeat Steps 1-3. If you have a fast skill that you can use, cast it quick, but take in mind that you will need to guard after 1 second. If possible, don't stay in front of him as he WILL stun you and dash backwards, then shoot a volley of fireballs at you, where you are unable to guard at the time.

[NOTE: For people who doesn't know this, doing a perfect guard (Meaning Guarding for 0 HP loss) will speed up the cast of your next skill-startup. Basically this means that that your skill will start going off as soon as the Ougi animation starts. Ex. Perfect Guard a Kappa's trident, then use TB. Will see a significant difference when you normally TB and a perfect guard + TB.]

Known Melee Moves by Garg:

1. SMASH!: Slams his club of justice at the ground, dealing damage in its radius. It's not going to kill you if you have high HP, but he usually finishes it off with a swing to your face.
2. B*tch Slap: Swings his club in a 270 degree spin. Easy to Guard if you predict it.

Infernal Gargoyle's other BS moves:

1. Stun: Garg will quickly dash back. If you are right in front of him, roll. Behind or around him, Guard. If you are stunned, he WILL shoot fireballs around and you will be unable to guard it.(As mentioned above) If everyone in your party dodges that stun, the fireball animation will still occur.
2. Fireballs(Normal): Easy. Guard right before it hits you.
3. Throwing da beating stick: Garg will throw his BS stick of justice, one shotting about everyone. Just Guard when you see it being thrown at you. Do not roll as the stick of justice actually closes on your location.
4. Rapid fireballs + Many Small AOE ground explosions: DO NOT ATTEMPT TO DODGE THE FIREBALLS! They will simply follow you till your die wondering wtf happened. With the right skills, you can perfect guard all of them(Or at least tank some damage). If possible, you should guard about 1 second before the fireball closes in on you. I'm not going to talk about the AOE explosions on the ground since its obvious that its a trap + easy to dodge.
5. Garg's BS Ougi: As you lower his life lower, you will notice Gargs movements change a little. This is relatively hard for people who don't anticipate this fast enough. You will hear a little sound similar to the Pipe 5 Boss (I found their base attack patterns similar, including the radius of Tentouki's stun) then a pillar of fire kills everything(pretty much Ougi Bursting Embers VI). This can also be predicted by the Infernal Gargoyle's hand glowing before it starts. Em... Just saying, if you absurdly close to Gargoyle when he does this... Better gtfo fast or if you even get lucky, roll/perfect guard that. (It's been done, kinda hard with the lag of this server)

tl;dr: Tell me if I'm missing something. Also, this information may be useless to you due to lag problems due to the BS of the server.

Edit:
1. Added info from SupremeTentacle.
2. Updated and clarified some information.

When the garg's about to use his ougi, his right hand glows for a bit. This can be observed when he's using it in the air too.

SupremeTentacle wrote:When the garg's about to use his ougi, his right hand glows for a bit. This can be observed when he's using it in the air too.

ty

Perhaps I should've put this in the Strategy and Guides section. lol