Quote Originally Posted by Ogeeogelthorpe View Post
This is wrong. Your character level is 9, and because both classes are 1/3 casters you would have the spell slots of a 3rd level FULL caster.
So your spell slots would be 4 1st level spells, 2 2nd level spell slots.

At level 20 you'd have the same amount of spell slots a level 20 arcane trickster or eldritch knight would have even though you're splitting classes because it's your total caster level that matters, not class level, when determining slots.

However, when determining what spells you can use/learn you'll be limited to what spell levels those classes can use at those individual levels instead of the spell slot level.
Level 9 arcane trickster can only learn level 2 spells. So an 11/9 split you'd be limited to 2nd level spells because both EK and AT only get 3rd level spells at class level 13.

Also of note for rogues, your sneak attack only triggers once per TURN. Not per attack. It will work on op attacks so sentinel is a good feat, as is warcaster. And if you use a blade coast cantrip like booming blade you don't get to multi-attack unless you're hasted. Worse, you won't get haste until level 13 arcane trickster.
And another note: Darkness and the spell darkvision do not syngergize at all. You need devilsight to see through magical darkness. You're better off with fog cloud at 1st level.

Honestly, this build, though it sounds interesting, takes the core elements of each class and throws them out. Eldritch Knights are among the tankiest of tanks in the game due to heavy armor, shield spells, cantrips like lightning lash and booming blade. Arcane trickster is one of the sneakiest characters in the game that can control the battlefield with a few well placed spells to stop an enemy in their tracks with suggestion, Tasha's hideous laughter, etc.

For the OP, I'd ask myself what I intend to bring to the party with this build, then I'd spec from there. Do you want to be one of the group's primary DPS? Do you want to be the skillmonkey? The tank? Rogue/fighter is a great combo for a damage dealer. Swashbuckler or Scout/battlemaster or Swashbuckler/samurai is incredibly potent. I just don't think an EK/AT combo is all that it's cracked up to be.
Howdy!

First, thanks for pointing out darkness vs darvision lack of synergy... Totally missed that. I might still keep those spells as they are super handy any way, but its good to know the mechanics!

As far as what I am bringing, well... background of character is a guy who was brought up as a fighter in his family, but was far more intelligent than the average folks in his town/family. Long story short, family was murdered, struck out on his own to find vengeance, joined a thieves guild to gain knowledge of adversaries and then began studying arcane arts on his own using his superior intellect to discover spells etc.

This turns him into a fighter/skillmonkey/skullduggerer with spells.

Note: I understand this is not the most optimized combo of skills, but its been fun to draw up and play through level 7! Good in a melee, spells augment offense, defense and sneakiness. Its a good time!