If you use Dismember on it, it is then a 1/1 with 3 damage marked on it, but this doesn't destroy it because it's indestructible. Indestructibility means two very specific (and narrow) things: it can't be destroyed by effects which say "destroy", and lethal damage won't destroy it.
What kills an indestructible creature?
A creature with indestructible can die as a result of anything that is not damage (Lightning Bolt) and does not explicitly use the word 'destroy' (Doom Blade). And of course, they can be exiled, returned to their owner's hand, or put back into their owner's library.
How do you destroy indestructible?
How to Destroy an Indestructible Creature
- Exile It. If you can't face your problems, send them somewhere else. ...
- Reduce Its Toughness to 0. ...
- Make Your Opponent Sacrifice It. ...
- Counter It.
- Enchant It.
- Discard It from Your Opponent's Hand.
- Send It to Your Opponent's Library.
- Bounce It Back to Your Opponent's Hand.
