Ragnarok Online Assassin Cross 99/70 Sonic Blow PVM Build

DISCLAIMER: It will only work with Soul Linker Spirit and Asperio/Elemental Convert and also of course EDP to one shot the monsters that you're after.

First, get another two account with a High Priest and a Soul Linker though I suspect you have the guild buff if so only make one alternate account for High Priest to use asperio on your Assassin(This is for hunting down shadow property/undead property monsters). For other elements such as Fire, Water and etc, use an alternate account for Sage to convert the elemental property of the weapon 

Second step take a look at these equipments and cards

Headgear:

Top: Leo Crown/Marionette Doll[1] + Vanberk Card/Any headgear with STR + Vanberk

Mid: AOG/Sigrun Wings/ Angel wing Ears

Lower: Pirate Dagger/Father's White Moustache

Armor: Bone Plate + Noxious Card

Weapon: Katar of Raging Blaze[3] Skeleton Worker Card 2x, Strouf Card 1x or vice versa/ Glorious Bloody Roar

Garment: Mufflers/Wool Scarf/Nidhaggor's Shadow Garb Giant Whisper Card/Whisper Card/Noxious Card

Footgear: Shackles/ Sprint Shoes[1] Antique  Firelock Card

Accessory:Bloody Shackled Ball

                 Ring of Flame Lord
                 Cold Heart
                 Thief Ring

You can take this guide further and one shot many monsters by just changing the element of the weapon and property/size cards.

These are my equipments, there's a noticeable difference in equipping shackles + bloody shackled ball as oppose to thief ring + cold heart but I haven't tested it out yet which one is better because it has a 8% increase in damaging medium-sized monsters for those two sets.

Assassin Cross Sonic Blow Guide Image

Assassin Cross Ragnarok Online Photo

Assassin Cross Sonic Blow Build 99/70