Progenitor Exarch

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.) When this Siege enters, exile target nonland permanent an opponent controls that isn't exactly two colors.

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for 1 or one mana of that creature's color.) Target creature gets +2/+2 and gains flying until end of turn.

When this creature enters, exile target creature an opponent controls until this creature leaves the battlefield. Plainscycling 2 (2, Discard this card: Search your library for a Plains card, reveal it, put it into your hand, then shuffle.)

Lifelink

Target creature or planeswalker you control gains protection from colorless or from the color of your choice until end of turn. If it's a creature, put a +1/+1 counter on it. (It can't be blocked, targeted, dealt damage, enchanted, or equipped by anything with that quality.)

+1: Create a 1/1 white Soldier creature token with lifelink. −2: Put two +1/+1 counters on target creature. It becomes an Angel in addition to its other types and gains flying. −6: Return all nonland permanent cards with mana value 3 or less from your graveyard to the battlefield.

Flying Whenever this creature deals combat damage to a player or battle, transform up to one target Incubator token you control.

Backup 1 (When this creature enters, put a +1/+1 counter on target creature. If that's another creature, it gains the following ability until end of turn.) Whenever this creature attacks, tap target artifact or creature an opponent controls.