Promise of Loyalty

Each player puts a vow counter on a creature they control and sacrifices the rest. Each of those creatures can't attack you or planeswalkers you control for as long as it has a vow counter on it.

Ghostly Prison

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Venerated Rotpriest

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
Whenever a creature you control becomes the target of a spell, target opponent gets a poison counter.

Innocuous Researcher

Parley — Whenever Innocuous Researcher attacks, each player reveals the top card of their library. For each nonland card revealed this way, you investigate. Then each player draws a card.
At the beginning of your end step, you may untap all lands you control. If you do, you can't cast spells until your next turn.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Sphere of Safety

Creatures can't attack you or planeswalkers you control unless their controller pays {X} for each of those creatures, where X is the number of enchantments you control.

Wilderness Reclamation

At the beginning of your end step, untap all lands you control.

Trostani, Three Whispers

{1}{G}: Target creature gains deathtouch until end of turn.
{G/W}: Target creature gains vigilance until end of turn.
{2}{W}: Target creature gains double strike until end of turn.

Seedborn Muse

Untap all permanents you control during each other player's untap step.

Hall of Gemstone

At the beginning of each player's upkeep, that player chooses a color. Until end of turn, lands tapped for mana produce mana of the chosen color instead of any other color.

Sol Ring

Duelist's Heritage

Whenever one or more creatures attack, you may have target attacking creature gain double strike until end of turn.