Ohran Frostfang is a lot of fun because it gives all of your attacking creatures deathtouch, which can turn an attack fatal very easily if Fynn is out
This is very relevant because you need characters in order to win the game the most common way to win is through accruing 20 lore
For 5, you get to deal 5 damage to any target, and for 8, you get to deal 10 to two targets, and so on as you scale up on mana
As Gavin Verhey explains, there are four Commander decks in all, and each deck comes with at least two different creatures that can command that deck, and for this set, you have your choice of a hero (each of the four heroes are in an adventuring party) OR a fearsome monster
Since Terra doesnt bring the reanimated creature back tapped and attacking, its a fundamentally less aggressive commander, but the lower mana cost to reanimate the creature gives you more flexibility on the turns you use the ability
Much like Derevi, Oloros design space would be revisited once more in a more fun, but still very dangerous, manner