Done Framedrop and reed blocks appeared

is railcraft in that pack

 

Yep

 

im going to say they were railcraft invisible heat blocks that look like air blocks.. they appear when you walk through an area although you cant see them.

 

from the video it does seem like they follow "paths" is some areas.. like someone has flown throug there and left a trail of those heat blocks you mention.

 

Summing up for those who will read this long multi-topic thread:

About the "Reed Block Wall" blocks from Botania "randomly" appeared in Overworld Node 1 and 2:

Infact it occurred shortly after the update to Direwolf 1.7

Infact all of those Reed Wall Blocks spawned only where there was "air" and nothing else before

Infact those blocks are invisible trails left by us players going around chests, around the Twilight Forest Portal seen on video, along my pier, in my vessel-base, etc.. (Railcraft mod makes "residual heat invisible blocks" to track player's movement by Trackman's Goggles

About the framedrop:

About the strange creature on the video:

Infact, in this 1.7 updated pack, the modder have increased its spawnrate very much (direSlimeChance=0.65, if I'm correct)
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So... Now it's all clear (each mystery revealed): again, thank you SO MUCH to everybody!