Bear Umbra

Enchant creature
Enchanted creature gets +2/+2 and has "Whenever this creature attacks, untap all lands you control."
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Druids' Repository

Whenever a creature you control attacks, put a charge counter on this enchantment.
Remove a charge counter from this enchantment: Add one mana of any color.

Nature's Will

Whenever one or more creatures you control deal combat damage to a player, tap all lands that player controls and untap all lands you control.

Aggravated Assault

{3}{R}{R}: Untap all creatures you control. After this main phase, there is an additional combat phase followed by an additional main phase. Activate only as a sorcery.

Najeela, the Blade-Blossom

Whenever a Warrior attacks, you may have its controller create a 1/1 white Warrior creature token that's tapped and attacking.
{W}{U}{B}{R}{G}: Untap all attacking creatures. They gain trample, lifelink, and haste until end of turn. After this phase, there is an additional combat phase. Activate only during combat.

Grand Warlord Radha

Haste
Whenever one or more creatures you control attack, add that much mana in any combination of {R} and/or {G}. Until end of turn, you don't lose this mana as steps and phases end.

Faeburrow Elder

Vigilance
This creature gets +1/+1 for each color among permanents you control.
{T}: For each color among permanents you control, add one mana of that color.

Sword of Feast and Famine

Equipped creature gets +2/+2 and has protection from black and from green.
Whenever equipped creature deals combat damage to a player, that player discards a card and you untap all lands you control.
Equip {2}