They can be a variety of different things, from facilitators to get to Fusion/Synchro/Link monsters, or they can be boss monsters in their own right
If you sacrificed an Angel to pay the cost of Shilgengar's second ability, use the toughness of that Angel as it last existed on the battlefield to determine how many Blood tokens to create
What's so special about this
For rule of the Aldering Forest, Numstail stole the acorn from Nestwind, who stole it from Brankie, who stole it from Lightroot, who stole it from Leafpaw, who stole it from Darkfur
These large sets usually contain too many filler cards and drive up the price of valuable cards due to relative rarity
there's even the quick effect that you can activate when your opponent activates a spell or trap card or effect and if that happens, deal 1200 more damage to your opponent