To greatly benefits from this card, proper utilization of XYZ monster will do the trick. A hand with 2 fusion monster will enable you to summon 2 cards, and you will be able to fuse them together to special summon other fusion monster.
Special Summons from your hand
"You can Special Summon 1 Level 4 or lower Union monster"
Union monster? What does this mean?
"Union" is a monster-type or what?