My gate is asking for 100 blue butterflies, where to get them?

There is a portal to the left of that gate your are trying to open. It's on of the portals that give you tokens when you complete it that's on the 12 hour cool down. About 2/3rds of the way thru there are tall clumps of grass with butterfly's flying around it, you get the butterfly's by chopping theses down. They require a level 31 sword to chop. Hope this help! If you need more info let me know in the comments and I'll try to help as much as I can!