If a creature with trample you control would deal combat damage to a blocking creature while you control Angrath’s Marauders, you must assign its unmodified damage. For example, a 3/3 creature with trample blocked by a 2/2 creature can have at most 1 damage assigned to the defending player. It will then deal 4 damage to the blocking creature and 2 damage to the defending player.
If an effect such as that of Chandra’s Pyrohelix asks you to divide damage among targets, you must divide the unmodified damage before doubling it.
If you control a second Angrath’s Marauders, damage dealt by sources you control will be multiplied by 4. If you control a third, it will be multiplied by 8, and so on.