While he doesn't do a lot on his own, the extra card advantage is crucial and the access to win-condition cards like Underworld Breach is vital to closing out a game
Sen Triplets Sen Triplets is among the most popular Esper commanders thanks to its ability to steal your opponents resources if they let you untap with this trio
Limited supply from Championship events makes it a high-demand card among collectors
For example, the Adventures in the Forgotten Realms Set has over 400 cards in the set
Creature Crystalline Giant At the beginning of combat on your turn, choose a kind of counter at random that this creature doesn't have on it from among flying, first strike, deathtouch, hexproof, lifelink, menace, reach, trample, vigilance, and +1/+1
Since it's so low, you can copy multiple artifact abilities in one turn without investing a ton of mana, so you can hold it for other spells and interactions