Demi-Lich's Phylactery

You attempt to become a Demi-Lich using a Phylactery which grants immortality. This spell is weaker to the usual Phylactery creation in the sense that it does not make the user's body decay or appear undead. it is just given the long life of the undead. However, undead are friendly to the caster. The Spell is used by spending 1 hour prepping the runes and siguals and components. the first 4 hours of the spell you are using the 120,000 Gold to form a copartment for some of your life force to be stored in. If you choose to make one compartment for your soul to go in, you must take 2d10 necrotic damage and an extra 1d10 nectrotic damage per compartment. The Damage dealt by the creation will not loose your concentration.  for the next 4 hours, you then must draw the blood of a living sentient creature and mix it in with the posion. you first drink half of the solution and then pour the rest of the solution onto the compartment. you take 2d4 acid damge and also 1d10 necrotic damage as some of you is infused to the compartment. the sentient craetures body is disintegrated and soul is infused into the runes and siguals of the compartment which is what makes it a magic item.  once the spell has finished and a Phalactery has been created, the caster is immortal as long as the phalactory is intact. 

Designing your compartment 

the compartment can be anything between a amulet to a tombstone, as long as it is hollow in the middle for the life force to be stored. you can customise the design however you wish by adding in enchantments to protect it and other defences.

The phalactery

whilst the phalactery is intact, the user is granted immortalty. the casters body can be destryed but it will apperate in 5ft next to the Phalactery upon the prior bodies death. the equipement and magic items or any objects on the prior body will also be destroyed but re-apperate on the next body of the caster. the casters next body will spawn immediatly upon the priors death. if the phalactory is destroyed, the caster takes 1d10 nectrotic damage and is no longer immortal.

One or more phalactery's 

If the caster has more than one phalactory, all the phalactorys must be destroyed to stop the casters immortalty, for example, if the villain has 3 phalactery's and you destroy 1; then the caster will still be immortal, same for if you destroy 2. as long as 1 phalactery remains, so does the casters immortalty. if one of the phalactory's are destroyed however, then the caster takes 1d10 damage.

other pro-longing life effects

A clone of the caster from the clone spell can be active whilst the the Phalactery's are active but only as a last resort if the Phalactery's are destroyed and the character dies, then the soul can be re-animated into the clone body.

Benefits of the Phalactery

The caster gains immortalty, wild undead that are not commanded to be hostile to the spellcaster will be friendly, you also gain 1 Legendary action  per round. these types are listed below. you regain all legendary actions at the start of your next turn.

Cantrip- you can use one cantrip at the end of another creatures turn 

Counterspell- you can use one legendary action to counterspell an income spell attack but at a 3rd level