I just used the search function for this and i couldn't find an answer. When can i tribute the 2 PYRO monsters for Gaia souls effect? Im pretty sure its only Main Phase 1 or 2, but it seems almost like you could do it during your battle phase.

EX: Summon Gaia soul, have Thestalos and Flame ruler out. All in atk position. I attack their face down card with thestalos, its spirit reaper. I then tribute flame ruler for Gaia effect and attack his reaper for 2800 damage (because of trample effect). end turn and Gaia goes boom.

Gaia Soul the Combustable Collective is Spell Speed 1, and can only be used in Main Phase 1 or 2. Unless specifically stated (or implied by how its effect works), all monster card effects are Spell Speed 1. They simply don't print "only during your Main Phase 1 or 2" because the cards that aren't Spell Speed 1 have effects denoting that they are Spell Speed 2. If I'm confusing you, please tell me, the way I posted it, I started confusing myself. :p

Ok, thats what i figured. O well, Gaia soul could have been better, but there nothing i can do.