Pact of the Talisman

You can perform a ritual over the course of an hour to create a magical talisman symbolic of your patron. You can summon this talisman back to your hand as a bonus action if it is on the same plane of existence. While on the same plane, you always know the distance and direction between you and your talisman.
Acting as a conduit for your eldritch power, you can cast any of your known warlock spells through your talisman. Your talisman serves as an arcane focus, and when you cast a spell through it, the spell's range is determined from its location instead of your own. You can target the spell's effects as normal if the target is within your line of sight. Otherwise, any spell cast through your talisman without any targets within your line of sight will be unguided, and will instead be cast at a valid target or area nearest to the talisman following the spell's behaviour, or at the DM's discretion. If an unguided spell has no valid targets, the spell is wasted.
Your talisman can be subjected to a direct attack if it isn't being worn or carried. It has an AC of 10, 10 hit points, and immunity to poison and psychic damage. Your talisman is also immune to all damage from spells you cast through it.

Your Pact Boon

Your talisman may take many different forms depending on your chosen patron; here are some inspirations for your talisman's appearance:
The Archfey. Your talisman may appear as an inscribed stone, a petrified leaf, or a ring with the insignia of your patron's court.
The Fiend. A talisman from a Fiend may be an unholy symbol, a large fang or blood painted stone.
The Great Old One. Your talisman could take many different forms: perhaps a scrap of paper torn from a tome of secrets; a twitching eyeball pendant; or a small flickering lantern.