Mages of Mystralia (UP)

Have the following wand equipped: Igni Wand (this causes fire magic to do even more damage, which will already be stupid high from the spells I've set up and it also allows you to gather any red goblins in the area and kill them too, granted you shouldn't need them)

For this I found it easiest to use:
Fire based Ego with: Size (takes more damage so can set off more spells before it dies), Duplicate (to create the clown), Time (increases how long it stays out), Mastery (more damage dealt), Impact (so it does damage).

For the spell you use in Impact I would suggest:
Fire based Creo with: Swift (fires spell quickly), Size (gives a larger AoE), Mastery (more damage), Rain (best AoE), Time (spell lasts longer), Move (mixed with Rain gives this the best AoE). If you can get a bunch in front of it, just kite like 4-5 to it then face them and create a clone then run off behind the clone, one attack on the clone from any of those enemies will wipe them all out with a vengeance.

The best place to do this is in The Rise. There's a ton of goblins and monster rabbits to use this one.

For this achivement you need duplicate and impact and reverse to simply kill ten enemies.