Thallid Parasite

When Thallid Parasite enters or transforms the battlefield, return it to your hand unless you control a creature named "Infectious Thallid". Then, Threten 1. It gains Haste, Sporetouch and Provoke.
As long as you control a creature named "Infectious Thallid" Thallid Parasite has +2/+0 infect and "{1}{b}{g}: Thallid Parasite becomes an aura with "Enchanted creature does not untap on it's controllers untap step. Then each opponent creates a 1/1 green saproling."
On each upkeep, if no spells were cast last