Reliquary Tower

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

Once guarded by the Knights of the Reliquary, the tower stands now protected only by its own remoteness, its dusty treasures open to plunder by anyone.

Duskmourn: House of Horror Commander

When the aven scouts located the tower in Esper, the Knights of the Reliquary set off on a righteous crusade to recover their lost treasures.

Mystery Booster 2

Bloomburrow Commander

Modern Horizons 3 Commander

If multiple effects modify your hand size, apply them in timestamp order. For example, if you put Null Profusion (an enchantment that says your maximum hand size is two) onto the battlefield and then put Reliquary Tower onto the battlefield, you'll have no maximum hand size. However, if those permanents enter in the opposite order, your maximum hand size would be two.