When you attack with that weapon, you can use your Charisma modifier, instead of Strength or Dexterity for the attack and damage rolls. You can use that weapon as your Warlock Spellcasting focus. At 1st level, whenever you finish a long rest, you can touch one weapon, that weapon becomes your Soulbound Weapon until you choose a new weapon at the end of another long rest.
The influence of your patron allows you to mystically channel your will through a particular weapon. The following spells are added to the warlock spell list for you. The Eldritch Champion lets you choose from an expanded list of spells when you learn a warlock spell. The power that will ensure you can finish your tasks for your patron.
When you gain the power of an Eldritch Champion, you're gifted with a martial prowess that'll aid you in the battles to come, along with the power to help you strike down your foes, or protect you from upcoming harm. As their champion, you're bestowed with a power that will help you carry on your task and bidding for that being. It might be from a powerful Knights of the Past, or your power comes from a powerful General from The Abyss or the Nine Hells, or you gain your power through a deal with a powerful celestial that need a champion to do some biddings. Eldritch Champion power comes from a pact you've made with an otherwordly powerful warrior.