When combat damage is dealt by Terra, you may pay two mana to return a creature with three or less power from your graveyard to the battlefield tapped
If it lives to your next upkeep it allows you to put any creature from a graveyard into play under your control as a Phyrexian
Mono-Blue can control the table for ages, but at some point, you need a win condition
It keeps your hand full and your land drops consistent, especially against ramp-heavy tables
This is important, as whenever Nethroi mutates, its controller can return any number of creature cards with total power 10 or less from their graveyard directly to the battlefield.This can bring back a massive board state from the graveyard with the effect of a single card, potentially swinging the game in its controller's favor
Your opponents will quickly find themselves unable to compete