For example, it can't be used during the resolution of an ability that says "Counter target spell unless its controller pays 3." If an artifact you control has a mana ability with T in the cost, activating that ability while casting a spell with improvise will result in the artifact being tapped when you pay the spell's costs
Best Commander - Xenagos, God of Revels Xenagos, God of Revels gives haste and doubles power
It is a 2/2 with vigilance, so itll come down quickly and can attack and block without skipping a beat
If you exert a character card that fits your song's description, that song card can be played for free
(No) Totem Armor This is another Rise of the Eldrazi mechanic that was designed to make that set work
When he is good he is unreasonably good, making 5/5 fliers for no mana or life cost, just tapping some dorks, is hard to beat