Arbor Elf Though only untapping Forests is a tight restriction, the value of a 1-mana accelerant is hard to match
It has 6 different language versions of Monster and 3 special edition ones
I've won international championships and I've gotten top-four placement at world championships
Bruenor Battlehammer and Bureau Headmaster are other examples of cards that play a similar role, making the deck more efficient and explosive by allowing you to equip powerful gear quickly and without spending too much, if any mana
Brron allows you to discard when it deals damage
Sure, 4 mana is considered a little above average for reanimation strategies, but once you start pairing this commander with Training Grounds and Cabal Coffers, you can create several potent tokens a turn, then use your new Zombies to filter through the top of your deck during your upkeep to find the card you need to close the game