The Lands:
Ally Encampment
, Sliver Hive, Cavern of Souls
Lands that can pay for any color with a good percentage of the deck. The secondary abilities aren't half bad either. The Cavern only produces colors for creatures, but the other two can produce colors for the changeling noncreature spells too.
Swarmyard, regenerate that hits a bunch of your deck slapped on a land and activates for cheap seems like more than some fair decks would be able to put up with.
Seraph Sanctuary
, Seems pretty awesome especially in multiples. Cast a changeling dude, gain some life. In a bind for life while trying to wrap up a game? Ally Encampment could be a decent 1 of effect to bounce a creature to hand to cast it again for the few more life needed.
The Abusers:
Lord of the Unreal, Knight Exemplar,
Haakon, Stromgald Scourge
, and
Homing Sliver
Ok, all changelings getting +1/+1 and hexproof?? +1/+1 and Indestructible? Those are just gimmes and I shouldn't have to point out why they're in here... But Haakon maybe less obvious to some... Since changelings have ALL creature types, they are Knights as well, hence you can cast all the changelings from your graveyard; repeatedly if you wish. Homing Sliver makes all your changelings become 3 cost tutors for other changelings in your deck. Handy when you need a certain thing "RIGHT NOW".
The Abused:
So all of the changelings in the deck are abusable, but by using Shields of Velis Vel it can make ALL of your creatures abusable. Very very abusable...Haakon will hopefully enter play at some point and you could cast this many times from the graveyard... I am thinking about throwing a singleton Aetherflux Reservoir as an alt wincon, but haven't figured everything out yet. Inkmoth Nexus could also prove a very viable way to win when it becomes all creature types via either Amoeboid Changeling or Shields of Velis Vel.