Few questions..

1. Ambassador Divine/Custodian Divine, how rare are these, are they achieveable ingame?
2. What is the best fuse for Arb Tome & Arb Harp?

 

AMBA/SHEP DIVINE SETS (ASMODIAN) and EMISSARY/CUSTODIAN DIVINE SETS (ELYOS) are acquirable in-game using ABYSS POINTS + CERANIUM MEDALS. Those said items can be purchased in KATALAM NPCs and in DANARIA CAMP NPCs. They worth 1K VIP credits for every set on trading nowadays.

FOR FUSE:
ARB TOME should be fused with some kind of ATTACK SPEED TOME (TATAR, SHABUKAN AND RAVANGER).
ARB HARP should be fused with some kind of ATTACK SPEED HARP (EXALTED NOBLE KATALIUM HARP AND BRAZEN AEGIS HARP)

Note:
As a caster, an animation of every skill is finished before it takes into effect unless you use a technique called JUMP CUT that cuts the animation but do the skill perfectly.
Hence, ATTACK SPEED enables you to lessen the time of the animations for every skill. Thus giving you more faster animation.

 

or this if the NPC actually spawned
Moltenus' Spellbook

 

It is not an NPC. It is a mob/boss located in upper reshanta. However, I am not sure if it spawn on that area and if its item drop is set to have that tome since I haven't seen any kind of it's name in-game. Well, you need to give it a try tho.

 

as I said if the NPC spawns which it don't

 

Literally!

 

Thank you very much kind sir.. I just came back to Aion and not sure which are the best tomes to fuse with and stuff. Thanks.

 

Good to see you back in-game. Your always welcome bro. Always!