Araumi of the Dead Tide Recursion and self-mill decks are fun, especially if you use Araumi of the Dead Tide to bring back Mulldrifter and Massacre Wurm
If an effect causes a permanent to phase out "until" some event occurs, and that event occurs while Disciple of Caelus Nin is still on the battlefield, the phased out permanent stays phased out forever
Their spawn, although slightly smaller, are still enormous creatures
Will the Citadel player run out of targets or life before they find their wincon
While it does shut down the synergy with Brinelin, cards like Belbe's Portal and Aetherplasm can be used to play our biggest creatures for much cheaper costs than normal
The casualty ability is nice, but ultimately cards like this are too expensive for how little they accomplish when not used as a combo piece