Monster Destroyer
Kill 1000 Monsters
That's pretty self explanatory, just kill stuff


Dragon Destroyer
Kill 10 Dragons
Got kill dragon bosses, from stages 9, 10 and 12


Artifact Master
Collect 20 Artifact and Upgrade Complete
This will probably be the last achievement, you need to get all 20 artifacts and upgrade each to lvl 10, but its not so bad because once they reach max level the artifact stops dropping, so basically you have to keep redoing the stages until you catch them all


Enchant Master
Enchant 100 times
That's pretty self explanatory as well, just keep re-enchanting an item and you'll get it


Real Ending
Complete Last Stage + ?
To get the "real ending" you need to beat stage 12 after you gotten at least level 1 of all 20 artifacts


Air Combo Master
Air Combo 70 times
This is best done on a new game, select the knight for better armor, learn how to do air combos (arrow to right and left while enemy is in the air) gather a bunch of enemies in front of you (not bats or rats, the beetles+ are the best cause they tank way more than bats and rats), use the lightning bolt magic to lift them and do the combo. Its important that you don't upgrade your damage so you can do bigger combos without the enemies dying, gonna need to lift another enemy when the first one die and that's rng, but if you don't get it just upgrade your armor to gather more enemies in front of you at once and your HP if you have gems
Video demonstration:




Fairy Master
Solve Fairy's Quiz 15 times
Some faster moves faster than others, you'll need to get a really slow fairy for this, also its good to be on the first few stages so you don't worry about dying while paying attention to the fairy. A trick i was told can help is pausing, seeing what button needs to be pressed, unpausing pressing that button and quickly pausing again, but you'll still need a slow fairy


Candle in the wind
Use HP Potion 10 Times with 10% of Full HP
Self explanatory, just heal when really low hp


Death
Died 100 times
Self explanatory, just keep restarting stage 12 and not attacking anything


Millionaire
Get the money 10,000,000,000
You don't need to have 10b gold at once, you need to collect total 10b gold in your lifetime, which would be like 6~7b after you fully upgraded everything