“My good blade carves the casques of men. My tough lance thrusteth sure; and my strength is as the strength of ten, because my heart is pure.” -"Sir Galahad" by Alfred Lord Tennyson
You have drank from the Holy Grail, and the Lady of the Lake has shown you her favor, turning you into one of Humanity's greatest warriors.
You now have strength & endurance greater than Chaos Champions & Orc Warlords, skill & speed exceeding the greatest High Elven warriors, a powerful resistance to magic & the Warp, an aura that repels or destroys hostile undead or Daemons of low power, the charisma and beauty to court the Lady of Lake and make lesser men worship you as a demigod, and an eternal youth that can regenerate wounds and make the scars of war disappear.
There are also purely cosmetic effects like radiant halos of light, glowing eyes, and mist appearing underfoot everywhere you walk, but these can be toggled.
If you pray to the Lady, never use cowardly or underhanded tactics, and keep your vows, you may even receive the various boons her blessings grant. She can even resurrect you from the dead if the situation is truly dire. Try to stay on her good side.