Steamcore Scholar

Flying, vigilance
When Steamcore Scholar enters the battlefield, draw two cards. Then discard two cards unless you discard an instant or sorcery card or a creature card with flying.

Call a Surprise Witness

Return target creature card with mana value 3 or less from your graveyard to the battlefield. Put a flying counter on it. It's a Spirit in addition to its other types.

Guardian of New Benalia

Enlist (As this creature attacks, you may tap a nonattacking creature you control without summoning sickness. When you do, add its power to this creature's until end of turn.)
Whenever Guardian of New Benalia enlists a creature, scry 2.
Discard a card: Guardian of New Benalia gains indestructible until end of turn. Tap it.

Extraction Specialist

Lifelink
When Extraction Specialist enters the battlefield, return target creature card with mana value 2 or less from your graveyard to the battlefield. That creature can't attack or block for as long as you control Extraction Specialist.

Guardian of the Great Door

As an additional cost to cast this spell, tap four untapped artifacts, creatures, and/or lands you control.
Flying

Ledger Shredder

Flying
Whenever a player casts their second spell each turn, Ledger Shredder connives. (Draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on this creature.)

Harbin, Vanguard Aviator

Flying
Whenever you attack with five or more Soldiers, creatures you control get +1/+1 and gain flying until end of turn.