Here is the full list of all 19 Knightfall: Rivals achievements.
Win 300 total battles in either Casual Battles.
Win 300 total battles in either Ranked Battles.
Play the game for 90 days.
Unlock 300 total cards in your collection.
Upgrade your cards 300 times.
Play the game for 30 days.
Win 50 total battles in either Ranked Battles.
Win 50 total battles in either Casual Battles.
Open 100 total chests.
Win 10 total battles in either Ranked Battles.
Open 30 total chests.
Upgrade your cards 50 times.
Play the game for 5 days.
Unlock 50 total cards in your collection.
Open 15 total chests.
Win 10 total battles in either Casual Battles.
Upgrade your cards 10 times.
Unlock 20 total cards in your collection.
Complete the tutorial.