Ok, so why the devil is {Shardless Agent} so expensive???? Apologies if this was already posted somewhere.
See {baleful strix} another uncommon from the Planechase set that is expensive too.
The agent goes great in combo decks that are using the cascade effect to cast those 0 CMC bombs that you normally play with time counters on them. The cascade lets you play them for free without waiting for time counters to be removed.
It's a rather complex card to imagine. But basically {Shardless Agent} generates advantage with Cascade effect. You essentially get a 2/2 body, and possibly a Mox (Power 9) or another creature like a {Tarmogoyf}
Cascade will cast these for free with no time counters:
{living end}
{hypergenesis}
These are the 2 best targets.
A) There's only one way to get one, Planechase.
B) It's an arti-crit
C) Being a 3CMC, it'll skip past all 3+ spells and target your 2 or less. It's easier to plan exactly what it'll get and not prohibit higher spells. It's good for hitting removal spells etc.