Discard filler cards arent unheard of, they are used when printing sheets of cards to fill out the sheet when there arent enough cards to fill it
There weren't a lot of choices for artifact creature types at the time, so we went with a Golem because we liked the idea of him filling the archetypal role of the "gentle giant" (that is, a large, powerful, intimidating character that ends up being the kindest of the group)
These cards often require you to lower your opponents life points to 0 with them, and if you manage to do so, you actually win the match instead of just the single duel
SARs appear in roughly 1 in 6 boxes, SRs in 1 in 8 boxes, and URs in 1 in 12.5 boxes
In addition, the XY single block is a block with very poor draw/search support cards, but it can be said that the fighting type has an overwhelming advantage over other types just by the presence of this card