Vigilance
This creature must be blocked if able.
This creature can block an additional creature each combat.
". . . because to be honest, I couldn't tell you."
—Halana, Kessig ranger
(13/07/2016)
If each creature that could block Fibrous Entangler is tapped or is affected by a spell or ability that says it can't block, then none of them block. If there's a cost associated with having each of those creatures block, its controller isn't forced to pay the cost, so they don't have to block in that case either.
(13/07/2016)
If Tangleclaw Werewolf transforms into Fibrous Entangler while it's attacking, having vigilance won't cause it to become untapped.
(13/07/2016)
The defending player, not you, chooses which creature blocks Fibrous Entangler.
(13/07/2016)
Only one creature is required to block Fibrous Entangler. Other creatures may also block it, and are free to block other creatures or not block at all.
