At the beginning of your upkeep, sacrifice Serra Bestiary unless you pay.
Enchanted creature can't attack or block, and its activated abilities within their costs can't be activated.
10/4/2004 Does prevent the use of activated mana abilities with in the cost.
6/8/2016 Activated abilities contain a colon. They’re generally written “[Cost]: [Effect].” Some keywords are activated abilities and will have colons in their reminder text.