You'd better hope you grabbed some effective removal or you'll be taking a loss real quickly
Their activated abilities on both make the other more threatening in combat, either by making it more guaranteed to get damage in, or making one of them more evasive
The front half doesnt deal that much damage, and the back half gives the monarchy to another player, allowing the entire table to wear the crown before you get the chance
At less than fifty cents, Forgotten Ancient might be one of the biggest bargains available for this deck
Invigorate is one of the best combat tricks to use in conjunction with a Phyrexian Swarmlord
It was originally one of the main reasons for the banning of Cauldron Familiar, which could be repeatedly sacrificed with Witchs Oven to cause Mayhem Devil to trigger several times, destroying an opponents board and their life total with no way to respond