if I attack and other player blocks with a Elder Land Wurm and later I use mind control on the Wurm, can I attack with it?
if I attack and other player blocks with a Elder Land Wurm and later I use mind control on the Wurm, can I attack with it?
Yes. Once the Wurm has blocked, it loses defender for ever (or at least for as long as it's in play). Changing controllers won't make it gain defender again (summoning sickness will stop it from attacking that turn though).
Fluttershy is best pony.
What if after it blocks it gets exiled and comes back, like with momentary blink, does it still have defender?
Yes, then it will have defender.
Fluttershy is best pony.
If it leaves play, it will have no memory of anything it did before coming back into play.