Incubate is an ability that could appear on any card type, and will always be written with a number so, Incubate N. When an effect or ability tells you to Incubate, you create a colorless artifact token named Incubator, and put a number of +1/+1 counters on it equal to the Incubate number
Theres a slim chance birds could break out in Standard, especially after rotation, but this is hardly guaranteed
Now, again, just the Curse side of this isnt great, but when you staple the two cards together, you end up with a very playable card, especially in UW, which loves Enchantments
Durnan (and the Background) play great with the theme of the deck of playing cards from exile, but Id like to suggest that Durnan is awesome enough to play at the helm of his own Commander deck, or even in the 99 of other green Commander decks that lean into attacking a lot
RG decks love big power creatures so this will fit right at home in those builds