Trench-Foot

At the beginning of your Upkeep, put a -1/-1 counter on each Creature on the enchanted Field.
All Creatures that is on enchanted Field that has 1 -1/-1 counter on them have 1 less speed.
All Creatures that is on enchanted Field that has 1 -1/-1 counter on them cannot attack.
All Creatures that is on enchanted Field that has 3 -1/-1 counter on them are destroyed.