Grixis Polymorph

i wanted to try my hand at designing something that wasnt what people would expect, so I decided to try a variation on the polymorph. it is still a work in progress and any thoughts would be greatly appreciated. the basic idea is to control their mana early with contaminated grounds and spreading seas while using duress and blightning to manipulate their hand. ive decided on two ways to use polymorph: either the tokens generated by goblin assault, the dragon fodder in my sideboard or even activating the creeping tar pit and hitting that with polymorph. i have built all of this on a budget with the cards i own or have managed to trade for, if and when i can get my hands on more cards i will definitely try.