Hero spell

Name of Spell- Hero Spell
Training Cost (usually in elixir)- 400DE
Targets- Users troops
Effect Type- Troops in spell radius take no damage and increase speed and power for duration of spell.
Training Time- 3hours
Description- The alchemists have harnessed the power of dark elixer into a magical spell. The most bumble of archers becomes as strong as the queen
Research/Spell Levels- spell factory lvl6
Lab Level- lvl2 - lab 6
lvl3- lab 7
lvl4 lab 8

what do u think?

Could be VERY op unless this is very well balanced and has a short time. Of course, for it to be short enough itd orobaly end up being up