This is a concept I've been working on.
Dragonborn - cult of the dragon infiltrator. He was raised by a the cult to be an elite troop commander.
Patron - Tiamat
1 - Dragonborn fighter 4 (battle Master)/ Warlock 5 (Fiend). I haven't decided what to do for the rest of the levels yet
Fighter at 1st level - heavy armor, greatsword prof (greatweapon fiighting style), Second Wind, Athletics and Con saves
Warlock 2nd level - Eldritch blast, temp hp, burning hands and the command spell
Warlock 3rd,4th, 5th & 6th Level, Pact Blade, Lifedrinker (Cha bonus to pactblade), Thirsting Blade (two attacks per action with pact blade), +2 to Strength, Agonizing Blast (cha bonus to EB), Misty step spell (great mobility)
Fighter at Levels 7, 8 & 9 - 3 Maneuvers (rally, Riposte, and Commanders strike), Great Weapon Fighter Feat, Action Surge
This is a pretty cool mystic warrior IMO, and it appears to be affective. I haven't tested it though