I have a question to a potential combo. I thought every combo would be listed at spellbook, but I couldn't find that. Therefore I doubt if this works.
On the field:
[[Persistent constrictor]]
At the beginning of each opponent's upkeep, they lose 1 life and you put a -1/-1 counter on up to one target creature they control.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)
[[Obelisk spider]]
Reach
Whenever this creature deals combat damage to a creature, put a -1/-1 counter on that creature.
Whenever you put one or more -1/-1 counters on a creature, each opponent loses 1 life and you gain 1 life.
[[Blech]]
Whenever you gain life, put a +1/+1 counter on each Pest, Bat, Insect, Snake, and Spider you control.
[[Viscera seer]]
Sacrifice a creature: Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
I sac persisten constrictor with viscera seer. Persistent constrictor comes back and it enters with a -1/-1 counter. This count as putting a counter on a creature, so obelisk spider triggers. Obelisks trigger goes on the stack and resolves after constrictor entered. I get 1 life, blech is triggered and adds a +1/+1 to constrictor. I sac constrictor again and repeat.
The only point i could imagine why this not works, is that obelisk is triggered before constrictor enters, but there is no sba check before constrictor enters, so it's on the field, when obelisk and blech resolves. Am I right?