Once you have sealed a monster soul, (it will tell you in chat "your monster soul has changed"), use the skill Soul Contract located in your ETC tab to form a contract with the monster.
Soul Contract costs sealed souls to use, and it can fail so you will have to use it again until you form a contract.
It has a 20% chance to successfully form a contract and once you have use Materialize Soul to summon the monsters soul. It will be fighting for you until it dies, and you can heal it and buff it.
Level 1: Duration 3 minutes.
Level 2: Duration 5 minutes.
Level 3: Duration 10 minutes.
Materialized Souls fully inherits the players stats * 2.
Str, Agi, Int, Dex, Vit, Luk
Basic Attack, MATK min & MATK max
Weapon Atk, Weapon Atk2
The size of the summon when using materialize soul has been reduced. Do note that this does not affect the stats of the summon in any way, it just affects the size.