Artful Takedown

Choose one or both —
• Tap target creature.
• Target creature gets -2/-4 until end of turn.

Archon of the Triumvirate

Flying
Whenever this creature attacks, detain up to two target nonland permanents your opponents control. (Until your next turn, those permanents can't attack or block and their activated abilities can't be activated.)

Aegis of the Legion

Equipped creature gets +1/+1 and has mentor. (Whenever it attacks, put a +1/+1 counter on target attacking creature with lesser power.)
Whenever equipped creature mentors a creature, put a shield counter on that creature. (If that creature would be dealt damage or destroyed, remove a shield counter from it instead.)
Equip {3}

Arrester's Admonition

Return target creature to its owner's hand.
Addendum — If you cast this spell during your main phase, draw a card.

Applied Biomancy

Choose one or both —
• Target creature gets +1/+1 until end of turn.
• Return target creature to its owner's hand.

Niv-Mizzet, Guildpact

Flying, hexproof from multicolored
Whenever Niv-Mizzet deals combat damage to a player, it deals X damage to any target, target player draws X cards, and you gain X life, where X is the number of different color pairs among permanents you control that are exactly two colors.