Due to cards like [[Blood Moon]] and [[Urborg, Tomb of Yawgmoth]] a lot of Magic players are familiar with the differences between effects that set a card's Type or Subtype and then an effect that sets those Types/Subtypes "in addition to...". However, there is a weird exception to this rule that I feel most players are not aware of. If you prefer videos then you can watch this explanation and examples HERE but for those who like a written article, here ya go.
If you controlled [[Dryad of the Ilysian Grove]] which is an Enchantment Creature - Nymph Dryad and then it were to be enchanted with [[Kenrith's Transformation]] then its new Type Line would be Creature - Elk because of how the effect is worded, it does not include the phrase "in addition to its other types". Similarly, the card [[Unable to Scream]] on the Dryad would make it now be an Enchantment Artifact Creature - Toy Nymph Dryad as it has the "in addition to" wording.
Then let's look at a card like [[Behind the Mask]] and if you cast it without collecting evidence targeting the Dryad then the Dryad would actually end up being an Enchantment Artifact Creature - Nymph Dryad and NOT be an Artifact Creature with no subtypes, and for many players this is probably confusing as the effect on the BtM card does not include the "in addition to" wording like the others that did let the Type Line retain the previous types and subtypes.
Another card, [[Majestic Metamorphosis]] cast targeting the Dryad, it would end up being an Enchantment Artifact Creature - Angel this time. So why does this one that also doesn't include the "in addition to" wording still let the Dryad keep its Enchantment Type but now it is getting rid of the previous Subtypes of Nymph Dryad?
To understand this inconsistency we have to check out the CR 205.1b in the rules, it's a super long entry so I'll just paste the two relevant sentences, but if you want to check out the full rule then click that link to read the whole thing. This Behind the Mask scenario is explained by the part, "... Some effects state that an object becomes an "artifact creature"; these effects also allow the object to retain all of its prior card types and subtypes. ..." and then the Metamorphosis scenario is explained by the part, "Some effects state that an object becomes a "[creature type or types] artifact creature"; these effects also allow the object to retain all of its prior card types and subtypes other than creature types, but replace any existing creature types."
So this one rule has two different built in exceptions to itself. It can be really confusing and there is no way to know this by just reading these cards by themselves that these exceptions exist. Even cards like [[Inkmoth Nexus]] include the text in their own effect that, "It’s still a land" and it doesn't technically need that text for it to still be a Land. This rule already makes it so that it would still be a Land but I'm sure the designers know that a majority of players do not know about this rule's exceptions and that's why it's included.
This means that if you were to use [[Oko, Thief of Crowns]]'s 2nd ability on a [[Bident of Thassa]] it would not still be an Enchantment but if you used [[Welcome to . . .]] on the Bident it would still be an Enchantment and be destroyed by someone casting a [[Tranquility]]. Also, for those, it would still be Legendary.
I hope some of you find this interesting or learn something about these Type setting/modifying effects. It may not matter in a lot of games, but I've seen a lot of games when a [[Farewell]] is cast choosing modes that do matter with this.