From 1d4chan

One of the many classes introduced in Spheres of Power, Mageknight is (unsurprisingly), a Gish class. Like most Spheres based classes, it boasts a high level of customization, with most class features being chosen by the player (their talents are gained at every even level and called "mystic combat"s) and are fairly generic without taking an archetype (for which they have many). As low casters (Half Caster), they are intended to be martial characters with some magical tricks, rather than potent casters themselves.

Like most Spheres classes, their tier is a bit difficult to pin down due to their level of customization raising the question of what "optimization neutral" puts them at. Their low CL making Legendary Talents effectively capstone only aside from Life (which they can take a mystic combat to make work for them as a Full Caster for that sphere only) and limited magic power will generally keep them out of tier 2 well optimized spherecasters with Legendary Talents allowed can reach. They most likely belong to tier 3 and 4.

The Classes of Pathfinder 1st Edition
Core Classes: Barbarian - Bard - Cleric - Druid - Fighter - Monk
Paladin - Ranger - Rogue - Sorcerer - Wizard
Player's Guide:
Alchemist - Antipaladin - Cavalier
Inquisitor - Oracle - Summoner - Witch
Class Guide:
Arcanist - Bloodrager - Brawler - Hunter - Investigator
Shaman - Skald - Slayer - Swashbuckler - Warpriest
Kineticist - Medium - Mesmerist
Occultist - Psychic - Spiritualist
Ultimate X: Gunslinger - Magus - Ninja - Samurai - Shifter - Vigilante
The Third Party Classes of Pathfinder
Psionics: Psion - Psychic Warrior - Soulknife - Wilder
Aegis - Cryptic - Dread - Marksman - Tactican - Vitalist
Path of War: Stalker - Warder - Warlord - Harbinger - Mystic - Zealot
Akashic Mysteries: Daevic - Eclipse - Guru - Nexus - Radiant - Rajah - Stormbound - Vizier - Zodiac
Spheres of Power: Armorist - Elementalist - Eliciter - Fey Adept - Hedgewitch - Incanter
Mageknight - Shifter - Soul Weaver - Symbiat - Thaumaturge - Wraith
Spheres of Might: Armiger - Blacksmith - Commander - Conscript
Savant - Scholar - Sentinel - Striker - Technician
Champions of the Spheres: Prodigy - Sage - Troubadour - Dragoon - Mountebank - Necros - Reaper - Warden - Crimson Dancer
Pact Magic: Pactmaker (formerly known as Medium)