Doodle God Blitz HD

Here's all combinations for unlock tihis achievement:

Combine Philosopher's stone and Water to make Beer.
Combine Philosopher's stone and Metal to make Gold.
Combine Philosopher's stone and Egg to make Dragon.
Combine Philosopher's stone and Poison to make Water.
Combine Philosopher's stone and Grass to make Flower.
Combine Philosopher's stone and Ghost to make Energy.
Combine Philosopher's stone and Werewolf to make Human.
Combine Philosopher's stone and Vampire to make Human.
Combine Philosopher's stone and Alcoholic to make Human.
Combine Philosopher's stone and Corpse to make Human.
Combine Philosopher's stone and Wood to make Tree.
Combine Philosopher's stone and Human to make Demigod.
Combine Philosopher's stone and Zombie to make Corpse

The following page lists all of the reactions necessary:

http://doodlegod.wikia.com/wiki/Philosopher's_stone

Update: September 18, 2015
This is now obtainable. You need to be on version 3.0.1.25 for this to unlock. Check your version before trying. If you already completed this you should be able to update and then complete another match with the Philosopher Stone and this should unlock.

At the time of this update I can't seem to get this new version to download so I haven't unlocked this. Hopefully this gets pushed to all users soon.

You can also reference this guide at Gamefaqs.

http://www.gamefaqs.com/iphone/998670-doodle-god/faqs/68098I

Edit 12 august 2018

If you're having issues try this:

Go back to Episode 2 and combine Quicksilver with a Demigod