Aggron sets his teeth and channels hard, boosting the mongrel against the stream of negative energy. The poor hound looks less enraged and increasingly unhappy about the swirl of magic pulsing around it.
Discard 1x Golgari Rot Farm, pump it again, still red.
Also I totally forgot about this ability. Props to the Filigree Sages, and I hope they haven't got much more mana...
Aggron's pupils begin to vibrate hard, as he continues to channel energy into the mongrel, countering the efforts of the battlemages with pure mental energy.
Discard another Golgari Rot Farm. Also, to cut this somewhat menial series of plays short, Aggron will keep trying to save the Mongrel until he runs out of rot farms, discarding each in response to a Battlemage activation. He's got two left, after this one.
No more effort is needed. The vedalken abandon that plan, seeing as it's not working very well, and use the last of their energy to re-empower a mage's staff again. The mage uses that opportunity to strike at the mongrel attacking the vedalken.
If the vedalken's going down, he's at least going to want to take the hound down with him.