Playing a deck with only evenconverted mana cost cards is going to lead to all sorts of curve problems
It quietly adds extra counters to your creatures or artifacts whenever they are distributed and can even tap itself to add one (which it then upgrades to two)
Call of the Ring adds a card-draw effect to re-assigning a creature as the Ring-bearer, at the cost of two life
In the Sword & Shield era, it became infamous for its Single Strike Roar an ability that lets you search your deck for Special Energy cards and attach them directly to your Single Strike Pokmon
Summon: Yojimbo and Summon: Ixion are probably the nastiest to keep around, as both of them have a Chapter I that lets you exile something, and if youre doing that every single turn, your opponents are going to be in trouble
The downsides of Calamitys Wake are that its useless against creature-based strategies and it also exiles the graveyard of the person who cast it