While this isn't quite a howling mine, it still lets you see more cards, and helps the Possessed Portal lock in that they don't draw, but they discard.

Quite the silver bullet it this deck. Finds like 13 cards, most notably Temple Bell, Back to Basics, Pulse of the Grid and Wipe Away.

A blue Explore. But, with Howling Mines, or planeswalkers, it gets crazy.

Some solid synergy with Tomorrow, Azami's Familiar in that with her out, it basically becomes a Vampiric Tutor.

Seems not great compared to the other mana rocks but I've lose too many games to Infernal Darkness and Contamination to not run this.