Like if you need extra bodies to go wide to win the game, or if you need those bodies to block Weve seen this card before, more or less, and in the right deck it can be a pretty good way to end the game, as turning off all blocking can really allow you to do a ton of damage
For Gandalf specifically, it helps that he was a powerful wizard, which opens up itself to lots of fun card designs, and that his character evolves significantly throughout The Lord of the Rings, Turian explains
In addition to being basically a Fusion-Equip-Spell Card, the card also has a die roll effect where when the Monster it's equipped to battles another, you roll a 6-sided die and your opponent's Monster will be banished for that many of your opponent's turns until the first Standby Phase after the last turn of the effect
What at first seems to be a flavorful uncommon that helps Blue decks ramp a bit quickly spirals into a rules rabbit hole once you ask a simple question: How does she work with Clones
Removal like Mortality Spear, Anguished Unmaking, and Infernal Grasp keep threats in check, while protection pieces like Shalai, Voice of Plenty and Swiftfoot Boots safeguard your key creatures