Sir Galahad is a King Arthur prestige hero and is unlocked at 150,000 prestige.
Unit Type: Lord's Retinue - Mounted unit that has high block, dodge and critical strike rate.
Stats: High Bravery; High Tactics; Average Magic.
Initial status is 76 bravery, 84 tactics and 57 magic and has a unit count of 410.
Sir Galahad is a step up from Alfred & Attila. His gambit, Shattering Thrust, attacks in the same pattern as those two heroes but he has a chance to stun his targets. The stun happens about 1/3 to 1/2 of the time and disables the affected targets for 1 turn.
Sir Galahad is better than Attila and Alfred for his high unit count and growth as well as slightly superior stats and unit type. His gambit attack deals 10-20% less damage than Attila but his gambit's status effect (stun) can be more valuable than Attila's extra damage.
Sir Galahad works well as a main attacker up through Trojan Warriors & Hellenic Offense campaigns. He loses value around the end of Hellenic Offense and you will want to either earn a lot more prestige to use Lancelot or King Arthur or simply out level the opponents.