Here is the full list of all 24 Whispike Survivors - there are Sword of the Necromancer achievements.
Get all the Feats
Survive in Alas Forest for 5 minutes
Survive in Mount Lisad for 7 minutes
Survive in Suib's Maw for 9 minutes
Survive in Raen's Ravine for 12 minutes
Get a Whispike with 10 attributes
Get a Whispike with 10 attributes at level 10
Stay still for 30s
Find the Sword of the Necromancer
Accumulate 10000 units of manure
Have something planted in all your farm plots
Kill 20 monsters with a single Pafi shot
Level up a Whispike to level 10
Pass the attributes of a rotting Whispike to a new seed
Get a Whispike's Whip to the max rank
Get your Speed to the max rank
Get a powerup from a Lootbox
Face the Necromancer for the first time
Get 20 heart drops in a single playthrough
Equip the 3 types of magic at the same time
Get your first hybrid Whispike
Plant your first seed
Use manure to get a Whispike to its next stage
Play for the first time