Another day, another (P2W) update (no Mystic Summon for now 
).
But I improved my predictions by including the variant identification for the Costume Chamber, Tavern of Legends, Covenant and Treasure quests, for example (with some teasers for May; in bold font for demonstration purposes):
- Tavern of Legends (Seshat variant) Apr 05 07:00 UTC (3 days): featured heroes: Ramona (new), 2 user-selectable featured heroes; no (other) new hero
- Costume Chamber (Isshtak C variant) Apr 08 07:00 UTC (3 days): featured heroes: Richard C3, Khagan C3 (new) + the introduction of (new): Cyprian C3, Kelile C3, Belith C2, Graymane C2
- Treasure Quest (Legendary Troops Coins variant) Apr 18 07:00 UTC (1 days): no-summon-gate event; featured families: Niflheim Realm, Grimforest Family, Muspelheim Realm
- Tavern of Legends (Hel variant) May 03 07:00 UTC (3 days): featured heroes: Mistra (new), 2 user-selectable featured heroes; no (other) new hero
- Costume Chamber (Jahangir C variant) May 06 07:00 UTC (3 days): featured heroes: Isarnia C3 (new), Leonidas C3 + the introduction of (new): Gormek C3, Little John C3, Berden C2, Hawkmoon C2
- Treasure Quest (Ice Trainers variant) May 16 07:00 UTC (1 days): no-summon-gate event; featured families: Underwild Family, Sun Family, Vanaheim Realm
Sadly, no Covenant Quest to show in the example as it’s not scheduled yet but hopefully staff will schedule it soon enough. If you can think of other quests with variations that I forgot, please scold me haha.