Card Spotlight
A 12/12 trampler that costs {10}{G}{G} but costs {X} less to cast, where X is the total power of creatures you control. With ten power on the battlefield she costs {G}{G}.
Commander Spotlight
Ghalta, Primal Hunger ↗
A 12/12 trampler that costs {10}{G}{G} but costs {X} less to cast, where X is the total power of creatures you control. With ten power on the battlefield she costs {G}{G}.
See Ghalta, Primal Hunger's full stats and printings →
As the commander of Tramplesaurus Rex she is the payoff for the deck's whole plan: play mana creatures, play large creatures, then cast a 12/12 trampler for very little. The upgrade guide's warning applies directly: the deck commits everything to the battlefield, so a board wipe both removes the creatures and puts Ghalta's cost back up.
She fits green decks with a high count of large creatures, where she often costs two or three mana by the midgame. In a deck of small creatures and tokens with low individual power she stays too expensive to cast on time.
Garruk's Uprising ↗
Gives your creatures trample and draws a card whenever a creature with power 4 or greater enters, which includes Ghalta.
Overwhelming Stampede ↗
Gives the team trample and +X/+X equal to your greatest power, and with Ghalta out that is at least +12/+12.
Rishkar's Expertise ↗
Draws cards equal to your greatest power, which is at least twelve with Ghalta on the battlefield.
Heroic Intervention ↗
Gives your permanents hexproof and indestructible for a turn, which protects the board her cost depends on.
Ghalta is inexpensive. She has been reprinted many times, including Foundations, Commander Masters and now Tramplesaurus Rex, and premium Secret Lair versions are the only printings that cost noticeably more. The precon is a cheap way to get her along with the big creatures she needs.
Add up the power of every creature you control, and subtract that from the generic part of her cost. The reduction only removes generic mana, so she never costs less than {G}{G}. Two 5/4s bring her all the way down to {G}{G}.
For a deck that wants to put big creatures on the battlefield and attack, yes. She rewards the deck for doing what it already does, and a 12/12 trampler ends games fast. The weakness is interaction: a deck built around creature power has few answers to an enchantment, artifact or combo.
The commander tax adds {2} for each previous cast from the command zone, but that tax is generic mana, so her reduction applies to it as well. With enough power on the battlefield she still costs {G}{G} on a second or third cast.