What are -1/-1 counters in Magic The Gathering?

Question

i seen alot of them in Army Of Entropy, i like black and red so i wanted to know what it was.

Answer 1

Rules for counters:

If a creature is given a -1/-1 counter, place a counter on the creature (dice, penny, or whatever you want to use) and the creatures power/toughness changes.  If the creature was a 2/2, it becomes a 1/1.  If it becomes a anything/0, it dies.

The same works with +1/+1 counters.  A 2/2 with a +1/+1 counter becomes 3/3.

Another thing to note.  If a creature with a +1/+1 counter is given a -1/-1 counter, you just remove the +1/+1 counter from it.  The same works in reverse.

Answer 2

They give a creature -1/-1

People typical use coins to represent counters

Answer 3

they are when u subtract 1 from the power, and 1 from the toughness. For example is u put a -1/-1 counter on a 3/3 creature, it becomes 2/2.

Also, if you put a -1/-1 counter on a 1/1 creature, it dies