Barrage of Boulders was often excellent in Khans of Tarkir as it could function as both a removal spell and a win condition in the board stalls often seen in the format
But realistically, Mardu Siegebreaker is a 4/4 deathtouch haste that gives a creature you control pseudo-myriad, and thats a lot of damage coming out of nowhere
However, competitively speaking, PAF introduced very few cards which impacted the game
Its even better with Goblin Welder and co, who can scrap it before the end step trigger and bring it back again next turn
Creature - Archon Color tag templates(None) Bilious Skulldweller Deathtouch Toxic 1 (Players dealt combat damage by this creature also get a poison counter.) Creature - Insect Phyrexian Color tag templates(None) Blightbelly Rat Toxic 1 (Players dealt combat damage by this creature also get a poison counter.) When this creature dies, proliferate
It's not exactly the best red-zone threat we've seen in green for 6 mana, but it's serviceable