Here is the full list of all 50 Embers of Mirrim achievements.
Split 500 times
Enter your first Net
Enter Net 200 times
Use your first Rift
Use Rifts 500 times
Use your first Blast Rift
Use Blast Rifts 250 times
Use your first Slingshot Rift
Use Slingshot Rifts 100 times
Glide 100 times
Smash 20 Crystals
Enter the Spire
Gain the power of Dark Embers
Gain the power of Light Embers
Mirrim is born
Split for the first time
Complete The Spire
Use a Tungi for the first time
Survive the waterfall
Complete The Highlands
Use a Splitfire for the first time
Surive the first Thorn Chase
Complete The Weald
Ride the Whaleworm
Survive the second Thorn Chase
Survive the corrupted Whaleworm Chase
Complete The Blight
Survive the stalking Flarefly Queen
Use a Flarefly for the first time
Complete The Wasteland
Use a Tikeel for the first time
Complete The Breach
Complete The Descent
Defeat The Corruption
Complete Embers of Mirrim
Complete Embers of Mirrim saving all companions
Complete a Glyph
Complete 14 Glyphs
Complete all 28 Glyphs
Complete the Maple Leaf Glyph
Complete the Fleur De Lis Glyph
Complete the Mysterious "S" Glyph
Save Akat
Save Taka
Save Kiv
Save Vik
Save Inid
Save Dini
Save Ocu
Save Uco