"Why listen to the mumblings of wizards when the lash speaks true?"

Basandra, Battle Seraph

Flying
Players can't cast spells during combat.
{R}: Target creature attacks this turn if able.

Commander Anthology

Vintage Masters

Conspiracy

Commander 2011 Launch Party

Commander 2011

If, during a player’s declare attackers step, a creature is tapped, is affected by a spell or ability that says it can’t attack, or hasn’t been under that player’s control continuously since the turn began (and doesn’t have haste), then it doesn’t attack. If there’s a cost associated with having a creature attack, the player isn’t forced to pay that cost, so it doesn’t have to attack in that case either.

Players may still activate abilities during combat.

While Basandra, Battle Seraph is on the battlefield, players can’t cast any spells during the combat phase, including permanent spells with flash.