Ok, so I have listened to your suggestions. I think this is upgraded:
2 "Ghostrick" monsters with different original levels
During your opponent's turn (Quick effect): You can link summon this card. You can also use "Ghostrick" monsters that are face-down on your side of the field and/or attached to Xyz Monsters you control as material for this card's Link Summon. During the turn this was link summoned, your opponent cannot destroy "Ghostrick" or face-down Defense Position monsters by battle/effect, and they cannot be targeted by your opponent's cards/effects. "Ghostrick" Field Spells on the field cannot be targeted or destroyed by card effect. This card can be used for the xyz summon of a "Ghostrick" monster, except "Ghostrick Angel of Mischief".
Now it might be too op, so tell me how to improve it.