spells cost any player an additional ''Tap an untapped permanent you control'' to cast
your opponents may cast Myr spells with converted mana cost 4 or less without paying their mana cost

Converted mana cost: 2

Creature - Human Warrior (1/3, green)
When ~this~ is returned to its owner's hand, target player may pay 1GW. If that player doesn't, target facedown creature gets +4/+4 until end of turn
--His hair bruises more swiftly than the family shall
– Guike the Treacherous

Converted mana cost: 4

Instant (white)
each player may search his or her library for up to three basic land cards and put them into hand. Each player who searched his or her library this way shuffles it.

Converted mana cost: 7