The Second Generation of Phyrexian Praetors (DMU, NEO, SNC, ONE) Urabrask, Heretic Praetor Jin-Gitaxias, Progress Tyrant Elesh Norn, Mother of Machines Vorinclex, Monstrous Raider Sheoldred, the Apocalypse The Phyrexian praetors have a good ability for you and deny a good ability from your opponent in a mirrored way (e.g.: buff your creatures, shrink theirs, double your counters, halve their counters)
That gives you a sheer amount of flexibility in the Bellower that is hard to touch, and for that reason, I rate it highly
Like the Trademage, Forget lets you discard and draw cards, which is powerful when you have a Commander who is interested in the graveyard, discarding cards, or drawing cards
Some options help make additional land drops
Nasty sacrificial body to block and then tap and use his ability and stop an attack at the same time