Next to Basic cards, you may frequently get these cards when opening booster packs
Rotation helps mitigate extreme power creep by removing older, potentially weaker cards, ensuring a more balanced playing field
If you want, you can turn it into Isilu, Carrier of Twilight, which gives your creatures persist
As a third point of reference, here are all the Pioneer-legal cards printed each year (the blue bars), and the Pioneer-legal original cards (the red bars) released since 2013: Again, a similar trend: a slight increase in non-reprint cards, and a large increase in the number of reprints
Any card that looks at cards in graveyards looks at any or all your graveyards
Giant Adephage makes 7/7s with trample, Omnath, Locus of Rage makes 5/5s that will deal extra damage when they die, and Crested Sunmare makes 5/5s just for gaining life