If has a fyreslayer army i move my banner guy with nullisidian icon , can i try to ignore a spell that has already affected my unit ,since the effect apply in the current phase , my opponent cast a aura spell on a terrain and the effetc is when your within 3 of that terrain you can retreat and run, i a unit that i want to retreat , so i move my nullsidian banner to place it under the effect of my banner to roll the 4+ to ignore the effect that i can't retreat , is that legal ?