An interesting nuance to ZZ'Rot

The spawn frequency on portal is fast enough and the zerglings' health is high enough that you can actually halt a wave of minions from behind by keeping them all perpetually aggroing the zergling. Because minions move relatively slowly and since people only look at the minimap for a moment, halting the wave really doesn't look any different from a normal wave of minions unless you are consciously comparing it to other waves. Thus, unlike Promote it attacks the rear of the wave without itself being in direct harm. And if people notice that a lane is being pushed by the enemy naturally, they are going to go to the front of the lane, expecting to clear the wave and therefore push. Because it's rare for someone to go into the lane itself when deciding to push mid/late game, they will most likely not stumble upon the portal.

Kinda cool portal can do more than simply siege the enemy; it can also freeze waves, too.

Your portal is basically proxxy farming like Singed. Except there's almost no indication it's there, so no one knows wtf is going on.