The rules for Trample are more important in this situation:
Popular Commander Magic: the Gathering decks with prices from the latest tournament results. Destroy target non-Swamp land. If that land was nonbasic, Choking Sands deals 2 damage to the land's controller.
702.18b The controller of an attacking creature with trample first assigns damage to the creature(s)blocking it. Once all those blocking creatures are assigned lethal damage, any remainingdamage is assigned as its controller chooses among those blocking creatures and the player orplaneswalker the creature is attacking. When checking for assigned lethal damage, take intoaccount damage already marked on the creature and damage from other creatures thats beingassigned during the same combat damage step, but not any abilities or effects that might changethe amount of damage thats actually dealt. The attacking creatures controller need not assignlethal damage to all those blocking creatures but in that case cant assign any damage to the player or planeswalker its attacking.
Mtg Deal 2 Dmg To Land Controller Pc
Mtg Deal 2 Dmg To Land Controller Download
So the Primordial Hydra will assign 2 damage to the Etched Champion (because that would be considered lethal damage) and is then able to assign 22 to the defending player.