Mono-Red Sligh is a fast burn deck, but it does run 2 Sulfuric Vortex, an enchantment that deals 2 damage to each player at their upkeep and stops all lifegain. That shuts off Ravenous Baloth's life gain and speeds up their clock, so Tranquil Domain comes in as a live answer. It destroys all non-Aura enchantments, so hold it until Vortex is on the table, and remember it also destroys your own Pernicious Deed if that is out. Tormod's Crypt comes in because Grim Lavamancer needs to exile two cards from their graveyard for each activation, and Barbarian Ring's threshold ability needs seven cards there. Exiling the graveyard cheaply shuts both off. Duress comes out because it only takes noncreature, nonland cards, so it can't touch Jackal Pup, Grim Lavamancer, Mogg Fanatic or Ball Lightning, and the 1-for-1 trade does little to slow a deck with this many cheap threats. Haunting Echoes also comes out because it costs five mana and is too slow here, and Tormod's Crypt does the graveyard job far more cheaply. The plan is to survive the early burn and stabilize on the board. Wall of Roots (0/5) and Wall of Blossoms (0/4) block their small creatures well, and Ravenous Baloth is a big body, though its life gain does nothing while Vortex is out. Keep the full set of walls and Baloths in. Pernicious Deed is excellent at resetting their board of small creatures like Grim Lavamancer and Jackal Pup, since a low X is enough to sweep them.