Migospel is essentially the upgraded version of Migosp, much like it is the Hardmode version of Migosp in Undertale. Migospel can increase the maximum HP of an ally monster by 3, if the monster is damaged it will heal it for 3hp and still increase its maximum hp. This can also be added to non monster cards such as the bomb, like every other Battlecry ability, you cannot choose when to add the 3hp and must use the ability immediately after placing the card, so it is best to have at least one ally card on the field when you do this.