Kaalia is a veteran of the competitive commander scene, so you can expect many players to have a game plan when she shows up - removal, removal, and removal
(2005-08-01) If you choose Wall, then your creatures can still attack because creature types don't confer abilities such as defender (any more than, say, choosing creature type Bird would confer flying)
This card also has good Strength and Willpower stats of 6 and 5 respectively, while also giving the player 2 Lore points if they use him to go questing
Convoke Rules A keyword ability that lets you tap creatures rather than pay mana to cast a spell
And he comes with an interesting bounce ability
Synapse Sliver The first Sliver on this list, Synapse Sliver is a much-needed reprint, currently sitting just on the nose of $10