Technically unions. inspired by the onis

Eye of the Mountain
*4 Beast-warrior/Effect EARTH 1600/1400
If you control a face-up Rank 4 or lower EARTH Xyz monster, you can reveal another monster in your hand to attach this card from your hand to an EARTH Xyz monster you control as its Xyz material. If this card is attached to an EARTH Xyz monster as an Xyz material, the Xyz monster gains the following effect: Once per turn, look at 1 random card in your opponent's hand. If it's a monster, send it to the graveyard.

Heart of the Demon
*4 Fiend/Effect DARK 1200/1800
If you control a face-up Rank 4 or lower DARK Xyz monster, you can reveal another monster in your hand to attach this card from your hand to an DARK Xyz monster you control as its Xyz material. If this card is attached to an DARK Xyz monster as an Xyz material, the Xyz monster gains the following effect: Once per turn, you can select 1 card in your opponent's graveyard. Discard a card with the same type as the selected card, then activate the selected card's effect. This effect cannot be activated if your opponent did not control a monster.

Mind of a Magician
*4 Spellcaster/Effect LIGHT 1900/1100
If you control a face-up Rank 4 or lower LIGHT Xyz monster, you can reveal another monster in your hand to attach this card from your hand to an LIGHT Xyz monster you control as its Xyz material. If this card is attached to an LIGHT Xyz monster as an Xyz material, the Xyz monster gains the following effect: When a spell card is activated, you can banish 2 spell cards in your graveyard to negate the effect, then your opponent may draw 1 card and reveal it. if it's a spell card, your opponent must discard it.

The Oni guy never came back. T_T

So they are like Union Xyzs?

yes.