A new and unique Champion suggestion
As the title says...
Name: Odessa, the Wandering Paladin
Role: Fighter (AP Duelist Juggernaut)/Mage
Lane: Top/Jungle
Range: 200; is a melee champion
Movement: 340
Mana: 500-840
Passive: Protection
When Odessa takes any physical damage or true damage higher than 10/20/30% (Levels 1, 8, and 16) of her current health, she reduces the excess amount by 80%
Q: Lunge (800 target range) (30/35/40/45/50 mana cost; 8 second cooldown)
Odessa lunges her spear forward, dealing 90/150/210/270/330 magic damage (100% AP scaling) to all enemies hit by it. It deals 60% bonus damage to minions and monsters
W: Empowerment (40/45/50/55/60 mana cost; 18/17/16/15/14 second cooldown)
Odessa empowers her next basic attack for the next 8 seconds, dealing 20/22/24/26/28% of the target's maximum health in magic damage (4% per 100 AP scaling) to an enemy
Basic attacks reduce Empowerment's cooldown by 2 seconds
E: Bravery (380 effect radius) (60/65/70/75/80 mana cost; 12 second cooldown)
Passive: Odessa gains bonus 50/55/60/65/70% attack speed
Active: Odessa taunts nearby enemies for 2/2.25/2.5/2.75/3 seconds; she then gains 30/35/40/45/50% Physical Damage Reduction (1% per 100 health) and her basic attacks deal 60/70/80/90/100 magic damage (10% AP scaling) for 8 seconds
R: Last Stand (450 effect radius) (100 mana cost; 80/70/60 second cooldown)
Odessa channels for 1 second and then slams the ground with her spear, creating an inescapable arena trapping everyone, ally and enemy, for 6 seconds. Odessa gains 40/50/60 armor during the time.
Her main/recommended build:

Her main weakness is magic damage/being immobile/easily kited and is a hard counter to anything that deals physical and true damage.
Due to the amount of reduction and bonuses in her kit, she won't have a need to build any resistances (but still need to build health).