A dense set. Blight and vivid are the two that change how you build; the rest change how you play a turn.
Blight newPut N minus-1/-1 counters on a creature you control. There is no toughness requirement, so you may overkill a 1/1 token, and it can usually be paid at instant speed onto something already dying. Only blight when you have a payoff.
Vivid newCounts colors among the permanents you control, zero to five. Most vivid cards are playable at two. Hybrid permanents count as both colors, so a two-color deck can reach a vivid count of five on hybrids alone.
ConvokeTap creatures to help pay. Summoning-sick creatures can convoke, so a fresh two-drop immediately helps cast something bigger. Best in defensive shells: cast at their end step so your creatures blocked first.
ChangelingEvery creature type, in every zone: battlefield, hand, and graveyard. So a changeling in hand pays behold costs, and one in the yard counts for graveyard type counts.
KindredA card type that puts a creature type on a noncreature card. A kindred Goblin enchantment counts as a Goblin card, but never as a Goblin creature.
Transforming faces the twistThe double-faced legends can only be cast from the front, and they transform only if you pay a cost at the beginning of your first main phase. The night side is a mana sink you unlock on your own turn, not a flip that happens to you.
BeholdChoose a creature you control of the named type, or reveal one from hand. Kindred noncreature cards carry a type, so they can be revealed too.
ChampionBehold, then exile the card you beheld; you get it back when the champion leaves. Temporary, with one trap: if the champion is countered, the exiled card is gone for good. Do not cast one into an open blue mana.
EvokeCast an elemental cheap and sacrifice it immediately. Here they care about the colors of mana you spent, so paying wrong throws the card away for nothing.
PersistReturns with a minus-1/-1 counter if it did not already have one. With counters everywhere, persist creatures often die already carrying one and never come back. Counter-removal resets them.