We envisioned the monsters so when you travel to the "future" you'd find their remains - the bones you get to when you go to the first teleporter, when you enter the teleport, you find the enemy where the bones were because you are now in the past. You can also avoid the second enemy by bypassing him in a secret wall. The rest of the enemies are a bit stale but they make you collect the potions so you survive.
Thanks for the feedback, I'm glad you liked the puzzles and secrets.