Here is the full list of all 34 Idle Champions of the Forgotten Realms achievements worth 1,000 gamerscore.
Gained 100,000,000,000 Gold over all adventures
Defeated 2,500 Monsters
Completed the "A Brief Tour of the Realm" adventure
Gained 100,000 Gold over all adventures
Defeat 25,000 Monsters
Defeat 250,000 Monsters
Defeat 1,000,000 Monsters
Unlock an event Champion
Unlock 3 event Champions
Unlock 9 event Champions
Gain 1e18 Gold over all adventures
Gain 1e25 Gold over all adventures
Gain 1e32 Gold over all adventures
Gain 1e40 Gold over all adventures
Complete Area 100 in any adventure or variant
Complete Area 150 in any adventure or variant
Complete Area 200 in any adventure or variant
Complete Area 250 in any adventure or variant
Complete 12 Variant Adventures
Complete 72 Variant Adventures
Use Minsc's ultimate attack
Manually attack monsters 250,000 times
Shoot down 1,000 crows
Complete 250 Free Play Runs
Complete 10 Free Play Runs
Complete 50 Free Play Runs
Purchase and assign a familiar
Gather 10B favor with Torm
Obtain a Shiny (silvered) loot item
Defeat a level 100+ boss within 10 seconds of starting the area
Complete 100 Free Play Runs
Complete 48 Variant Adventures
Complete 4 Variant Adventures