Face of the mountain and locket
FotM 
did properly execute minions. It did it a few time but otherwise it failed.
Locket 
failed to activate of 2 occasions.
I had no impairment effects on me
5 Comments
Relic Shield's execute only applies to melee autoattacks. If you were playing a ranged champion (i.e. Thresh, Janna), it will only activate if you last-hit normally.
FotM does not proc the execute with Thresh. It will still work if you last hit them.