Ravnica Allegiance

Angelic Exaltation | Enchantment | | Whenever a creature you control attacks alone, it gets +X/+X until end of turn, where X is the number of creatures you control. | John Severin Brassell

Sentinel's Mark | Enchantment | Aura | Flash Enchant creature Enchanted creature gets +1/+2 and has vigilance. Addendum — When Sentinel's Mark enters the battlefield, if you cast it during your main phase, enchanted creature gains lifelink until end of turn. | Zezhou Chen

Sky Tether | Enchantment | Aura | Enchant creature Enchanted creature has defender and loses flying. | Zezhou Chen

Dovin's Acuity | Enchantment | | When Dovin's Acuity enters the battlefield, you gain 2 life and draw a card. Whenever you cast an instant spell during your main phase, you may return Dovin's Acuity to its owner's hand. | Bastien L. Deharme

High Alert | Enchantment | | Each creature you control assigns combat damage equal to its toughness rather than its power. Creatures you control can attack as though they didn't have defender. {2}{W}{U}: Untap target creature. | Daarken