Tundra Wall is no joke for competitive players, either, granting a solid protection to Pokemon with Basic water energy attached, while Freezing Chill shuts off your opponents Pokemon from attacking altogether.
Rev, Tithe Extractor -- The anime-inspired artwork is fantastic, and with deathtouch and theft abilities in mono-Black, this looks like a fun deck to pilot
Meanwhile Coral Colony (and the slightly inferior Doorkeeper) are much easier to work into various decklists as a nice blocker and mana-sink mill source
(Each in the mana costs of permanents you control counts toward your devotion to blue.) At the beginning of your upkeep, scry 1
(Note that the cards in this example, Recycle Energy and Mr
Honorable Mention: Board Wipes Good board wipes are excellent removal spells, and are ideal for handling threats with hexproof or shroud (targeted removal, on the other hand, is useless in those cases)