Hello everyone, I am new to Pathfinder, playing for like 3-4 months and I've only played around a total of mere 20 sessions in two campaigns and some one shots. Magus is a class that has a lovely flavor in my opinion, offering some great character ideas like vengeance seeking duelist or chaotic courtesan rogue or some lawful gambling addict etc. alongside with a unique gameplay so that I love playing and building a Magus. I also am into learning the system as much as I can and see classes' capabilities so try to read guides or do my own builds from time to time with several classes and this is one that I think quite viable. So I wanted to share my latest build with you guys. But if I messed up somewhere with the rules or the build's viability, I would be more than grateful to hear them.
So this one is probably the rogue-est build I've ever created which is an Arcane Trickster one and I find greatly optimal since you can use several movement mechanics like Fly, Greater Invisibility or Dimension Door to deliver a Sneak Attack; it has some hilarious single target damage, but also does not suffer the Magus' greatest weakness of endurance with its focus on Arcane Pool enhancements which last 10 rounds for a single point, also the Frostbite spell which is a multiple-use touch-attack. Well, it does, but not as much of a standard Shocking Grasp one.
The build is built on Kensai Magus and Unchained Rogue using VMC ruleset to become a Sneakmaster Arcane Trickster. The build is utilizing VMC so well in my opinion that you really do not even shed a single drop of tear for the lost feats or arcana. Well, to be honest its combat is unfortunately quite focused on Frostbite, Arcane Pool, Greater Invisibility and Dimension Door and you would use many of your corresponding spell slots for it, which makes its combat kind of a One-Trick-Pony which I'm not actually proud; but it works well and you still have 2, 5 or 6 level spell slots for the utilities you would want to have for combats or social encounters (unless you spam Mirror Image from 2, lol).
The greatest reason I chose Kensai Magus is actually limited to Canny Defense because of I like Intelligence builds and spices, and it gives us a nice combat durability; Weapon Focus since the greatest suffering of the build is low BAB and Iaijutsu in order to successfully deliver Sneak Attacks in the beginning of the combat by catching opponents flat-footed. And the reason of Unchained Rogue was having Finesse Trainings for free alongside with nicely stacking Sneak Attack bonuses.
So the build is:
Race: Elf you may want to take Fleet-Footed alternate trait for additional Initiative since we don't have that much for Improved Initiative.
25-points buy
STR 8
DEX 17
CON 14
INT 18
WIS 10
CHA 10
Traits
Reactionary or Warrior of Old for the standard cheese.
Magical Lineage (Frostbite) for Rime Spell for some nice cozy debuff effect.
Magical Knack
Ancestral Weapon is one of the greatest traits specifically for this build since you really have low BAB and need that additional AR from anywhere you can get. That +2 bonus for a trait is just awesome. If you can only take 1 Trait, then I'd say this one should be your go-to and then Magical Knack/Magical Lineage and then Reactionary/Warrior of Old. Also there are some other great choices but Unchained Rogue Dip gives you many social skills as class skills so you would not need to worry about them. If you can get 4 traits, this 4-set would be your ultimate set imo.
Level Progression
1) 1 Level Kensai Magus + Rime Spell
2) 1 Level Unchained Rogue + Finesse Training (for Rapier)
3) 2 Level Kensai Magus + Finesse Training (for Rapier) [VMC] + Sneak Attack 1d6 [VMC]
4) 3 Level Kensai + Arcana (that would be the only Arcana you'll have until late levels, so choose it wisely but it really is not that gamechanging. I'm open for suggestions here)
5) 4 Level Kensai + Enforcer
6) 1 Level Arcane Trickster
7) 2 Level Arcane Trickster + Sneak Attack 1d6 [VMC]
8) 5 Level Kensai + Elemental Spell or Extend Spell
9) 3 Level Arcane Trickster + Dimensional Agility
10) 4 Level Arcane Trickster
11) 5 Level Arcane Trickster + Finesse Training [VMC] + Sneak Attack 1d6 [VMC]
12) 6 Level Arcane Trickster
I advise Quicken Spell at HD 13 and Spell Perfection for Frostbite at HD 17 but it may differ.
And you end up on 1 level Unchained Rogue + 9 level Kensai Magus + 10 level Arcane Trickster at HD 20.
At level 12, you get the 2nd attack from BAB and by using Arcane Pool for two enhancements like Flaming and Frost for 2d6 damage, use Frostbite for 1d6+12 damage, get 6d6 of Sneak Attack damage for weapon and added to 1d6+5 (Dexterity mod.) weapon damage you get average of 52 damage per hit, allowing you to deliver 104 damage/round and if you cast a Frostbite as part of Spell Combat it makes 156 damage/round.
When you reach level 20, you get 10d6 Sneak Attack bonus both for weapon and spell so it turns out to be 20d6 Sneak Attack + 3d6 Arcane Pool + 1d6+20 Frostbite + 1d6+7 Weapon = 25d6+27 (115 damage) per hit, also your BAB is 11 which grants you 3 hits and if you use spellstrike also that makes a 460 damage/round with a sneak attack which you can get via many spells.
As for the ability scores, I would say all-in to Dexterity after 1st level.
Also as for the items, my advices would be:
Pearl of Power, many, for obvious reasons,
Gloves of Spellstrike for some nice Dimension Door shenanigans,
Mithral Shirt as an early-mid game lifesaver with Spell Storing for some nice dirty tricks,
Rapier with Spell Storing as initial for flashy entrances, especially when combined with Dimension Door + Gloves of Spellstriking, Cruel as a nice addition since why would you want to just kill people when you can both sicken and kill them, lol. Keen is not that much of a necessity as for other Kensais since the build is not working around high crits but Sneak Attacks and they do not crit. So I'd say anything else for Attack Roll bonuses since we really need them. In the end, we cannot kill the ones we cannot hit unfortunately.
I hope that I'm not mistaken with the ruleset and the build is a useful for Magus players out there seeking a place in endgame or some nice abstract for suitable character types. As I said in the beginning, I would appreciate any feedback/criticism on my understanding of rules and build idea. ^^