Viking Hero

Watched the credits to the end

how to achieve this: click on setting in left bottom corner, than select "Credits" in right column and watch it till end.

Viking Legend

Started the game 30 days in a row

how to achieve this: After starting game for 30 days in a row just claiming daily reward and exiting when in menu achievement did not unlocked!
So my opinion is that you must play every day at least 1 map to get this achievement.

Backfire

Wizard killed by own Vortex

how to achieve this: Use Magma storm spell - Bright Wizard Cataclysm spell, it activates in your hand when you step on Arcane Fulcrum with Bright Wizard.
You can use Elven ruins chapter 4: after start go straight to arcane in front of you. Than end your turn you get "Power saver" achievement. Enemies will surround you and next turn go Fulcrum and than use the Magna storm spell.
To get maximum success rate, you can prior this damage your wizard with other wizard spell.

Arcane Magic

Vortex damaged 5 creatures in one move

how to achieve this: Use Magma storm spell - Bright Wizard Cataclysm spell, it activates in your hand when you step on Arcane Fulcrum with Bright Wizard.
You can use Elven ruins chapter 4 after start go straight to arcane in front of you. Than end your turn you get Power saver achievement. Enemies will surround you and next turn go Fulcrum and than use the Magna storm spell.

Snake eyes!

Rolled 1 on the die 2 times in a row

how to achieve this: you will get it eventually by playing the game.

Power Saver

Ended turn without using any power

how to achieve this: just end turn before using any spell.


Warrior Priest

Revived the same Wizard 3 times in an Arena

how to achieve this: you will get it eventually by playing the game. Or use area damage spells to damage your wizard repeatedly. And revive him each time.

Too close!

Your Wizard was killed by a falling Giant

how to achieve this: just stay with a damaged wizard next to giant(1 tile) and when you hit him with a damage spell he will fall down and he makes 2 damage to any nearby enemies or allies. So it is good to have only 2 health on you wizard to achieve this.

Friendly Fire

Killed an allied Wizard

how to achieve this: use area damage spell on any enemy when your allied wizard is standing in the damage area.