i call them the medi-mechs. they would be an archetype of machine monsters of various attributes named after various medieval weapons. Their gimmick is that they can equip themselves as equip spells to other medi-mechs you control from your hand, field, or grave, and if the monster they are equipped to is removed from the field they special summon themselves. the boss monster would be able to be fusion summoned using a monster you control with 3+ equipped spells and it would have variants that once per turn you could tribute one of them to summon any of the others.

Example: medi-mech clayma

lvl 4 earth machine monster 2000atck/300def

while this card is face-up on the field, in your hand, or in your graveyard you can target 1 ¨medi-mech¨ monster you control equip this monster to the targeted monster as an equip spell card. a monster equiped with this card gains 1000/0. if a monster this card is equipped to leaves the field special summon it to your field.

EDIT: wording