An useful early offence. 30 damage is alright, however Flame Drum just seems awful. If you don't have Magby (I don't even know if people still use that Baby Evolution Poke-Body anymore) under Magmortar, you have to discard 2 useful energies for 80 damage? The 80 damage is nice, however unless I have something to retrieve the cards, it's not that useful...
I'd regularly rate cards good, but I'd have to give this...
Wait! The Firestarter Blaziken and Infernape Lv. X could really use it. If I'm correct their attacks and poke-powers rely on fire energy in the discard pile. If combo'ed with those, Magmortar can prove decent.
However if it isn't with something that relies on discard piles or you can't get those 2 energy back, it's worthless if you don't have a Magby. Plus the retreat cost is quite high. The only useful thing really if you can't spare energies if you don't have Magby equipped to Magmortar, is to use Smoke Bomb and hope your opponent's next attack misses. That's pretty much the only thing that saves it except for the decent HP.
7/10