Source (The Seer Cycle - "[...] They were moved to uncommon, and a new cycle of one-shot spells took their place at common. The common spells had the same scalable effect as their respective Seer.")
Source (Use of Multicolor - Power Spell Cycle (Rare) - "I believe this cycle turned into the Ascendancy enchantments, such as Jeskai Ascendancy ." - Empires (Rare) - "[...] We went through many iterations, but the one we went with is a cycle of enchantments that cost the wedge's colors. [...] It's possible this is the cycle that became the Ascendancy enchantments.")
Le nom de la carte An Offer You Can't Refuse fait référence à une réplique du film Le Parrain, qui n'est pas la première apparition de cette expression (dérouler la "note" après "The trope name comes from the movie The Godfather [...]" pour en savoir encore plus après avoir suivi le lien), mais une des plus célèbres et qui lui a donné son sens actuel (attention, spoilers!).
Source 1 (Question #7 - "Invasion, made use of Unglued II's split cards") - Source 2 (#1) (tie) Split cards (3) - "Split cards were first created for Unglued 2, but eventually saw print in Invasion.")
Source (History Lesson - "[...] First up is part a cycle that I knew we had to do if we did an enemy color set. Magic has done a cycle of monocolored Dragons. It's done ally color Dragons. It's done Dragons in shards. It's done wedge Dragons. All of these even have legendary versions. However, there has never been a cycle of enemy color Dragons. (There have been a bunch of blue-red ones, though.) That is, until now. [...] There has to be a cycle of mythic rare enemy color legendary Dragons. [...] It turns out each of the colleges was founded by and named after a Dragon. [...] Click here to meet Velomachus Lorehold")