I'm sorry, there is not an item or an effect in the game called Beastman Sigil. There are Beastmen Seals, I'm not sure if that is possibly what you might've been asking about them. They are used 'for: BCNMs, Fields of Valor Notorious Monsters, Squintrox Dryeyes key items. Can be s'tored with: Shami in Jeuno
Sigil is in effect that you receive from your nation to accumulate points while doing battle, missions, quests, etc. Since the Beastmen are an opposing army that you can never ally with, there is no way to get sigil from them.
Please see links below for further info. If you get the correct name of the item or effect you have questions about, please return and ask with a new question. Skyfiredancer (talk) 18:37, May 17, 2017 (UTC)