I find it pretty fascinating how a few differences in the nature of construction provide a cascade of effects which result in significant differences to power levels of cards
After Ral walks to Bloomburrow and is turned into an otterfolk, many onlookers (who have no idea this isn't is natural form) comment on how he seems to keep forgetting he has a tail, as he repeatedly trips over it or smacks people in the face with it when turning
Continuous Spells: Much like the name implies, a Continuous spell is a spell card that, when played, stays on the field of play and has an effect that continues until removed by a players action - such as the use of a spell-destroying card like Mystical Space Typhoon
Dawn Dragster 1x Odd-Eyes Absolute Dragon 1x Norito the Moral Leader 1x Timestar Magician 1x Number 41: Bagooska the Terribly Tired Tapir 1x Evilswarm Nightmare 1x Accesscode Talker 1x Selene, Queen of the Master Magicians 1x Heavymetalfoes Electrumite 1x Crystron Halqifibrax 1x Apollousa, Bow of the Goddess Yu-Gi-Oh
The most likely reasons are if it's sacrificed, if it's legendary and another legendary creature with the same name is controlled by the same player, or if its toughness is 0 or less
While on this topic it should be noted that while the direct effect of card quality spells will be to increase the cost of your mill effects the reality is that it will likely reduce it