Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Mountain

Command Tower

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

Arcane Signet

The Face of Boe

{T}: You may cast a spell with suspend from your hand. If you do, pay its suspend cost rather than its mana cost. Activate only as a sorcery.

Mirror Box

The "legend rule" doesn't apply to permanents you control.
Each legendary creature you control gets +1/+1.
Each nontoken creature you control gets +1/+1 for each other creature you control with the same name as that creature.

Command Beacon

{T}: Add {C}.
{T}, Sacrifice Command Beacon: Put your commander into your hand from the command zone.

Island

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Sol Ring

Plains

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)