if Uncle Istvan is blocking a creature with trample, can any trample damage ever go through?
if Uncle Istvan is blocking a creature with trample, can any trample damage ever go through?
Yes. You only need to assign damage equal to the blocker's toughness - whether or not that damage is dealt or kills the blocker, the rest can trample over.
Fluttershy is best pony.
"Prevent all damage that would be dealt to Uncle Istvan by creatures."
Nothing about that sentence implies that trample damage is prevented. If a creature with trample attacks, and Uncle Istvan blocks, the trampling creature only needs to deal 3 damage before assigning the rest of its damage to the defending player.
Here's an excerpt from the Comprehensive Rules that helps explain this:
...When checking for assigned lethal damage, take into
account damage already marked on the creature and damage from other creatures that‘s being
assigned during the same combat damage step, but not any abilities or effects that might change
the amount of damage that‘s actually dealt.