Darksteel Colossus

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Indestructible (Damage and effects that say "destroy" don't destroy this creature.)
If Darksteel Colossus would be put into a graveyard from anywhere, reveal Darksteel Colossus and shuffle it into its owner's library instead.

Foundations

Wizards Play Network 2024

Secret Lair Drop

Magic 2010

Trample
Darksteel Colossus is indestructible.
If Darksteel Colossus would be put into a graveyard from anywhere, reveal Darksteel Colossus and shuffle it into its owner's library instead.

Darksteel

Trample
Darksteel Colossus is indestructible. ("Destroy" effects and lethal damage don't destroy it.)
If Darksteel Colossus would be put into a graveyard from anywhere, reveal Darksteel Colossus and shuffle it into its owner's library instead.

Lethal damage, damage from a source with deathtouch, and effects that say "destroy" won't cause a creature with indestructible to be put into the graveyard. However, a creature with indestructible can be put into the graveyard for a number of reasons. The most likely reasons are if it's sacrificed or if its toughness is 0 or less. (In these cases, of course, Darksteel Colossus would be shuffled into its owner's library instead of being put into its owner's graveyard.)