Sir Lancelot is a King Arthur prestige hero and requires 450,000 prestige to unlock.
Unit Type - Elite Cataphract: Reduced damage taken.
Gambit - Spectral Blitz: Deal Gambit and Spell damage to a target and the targets 1 space to the left, right and behind it.
Sir Lancelot is a mid game elite gambit hero. Being a gambit hero his Spectral Blitz can be dodged. However, the magic damage portion of his gambit attack bypasses Entrench. Sir Lancelot is a stronger version of Sir Balin with a higher Unit Count and Growth, Bravery, Tactics and Magic stats.
Like Sir Balin and Titus, you want to equip him with the best Mounts and Enchanted Items you can get your hands on. You'll also want to enlighten his Tactics and Magic stat primarily, Bravery takes 3rd place for enlightment.