Ruins Chamber 1 trick for professors
How to use the trick:
1) Knock out the first foe (can be done with one energy if you are strong enough)
2) Cast the deterioration hex to the other foe
3) Start the battle
4) Don't cast a spell
5) Cast protego when they attack. The hex will take the foe's stamina. The protego won't take your energy.
6) Don't cast a spell, cast protego.
7) The hex will knock out the foe.
8) You will win the challenge with spending very few energy.
If your initial focus is four and the foe gives you 2 focus (If doesn't then use the trick above) replace step 1 with these:
1) Cast the hex on the foe
2) do steps 3) to 7) of the first instructions
3) You will receive enough focus to cast another hex.
Also if you make your deterioration hex stronger it will be quicker. And you must be strong to lower the energy spent on step 1.
If you replace step 1 with the second instructions you can spend 0 energy!(My initial focus isn't 4 so I didn't tried to replace yet.)
These can be done at ruins 11-111 too with a few energy. Also you must be strong enough to deal with the damage from the hexed foe.