I think we should have some more threshold Discovery cards.

Isn't this a bit OP at this mana cost and as a common though? Even without the Discovery part. +5/+3 for 2 mana is a lot.

Red doesn't usually pump toughness, and when it does its only like +1 or +2. Few exceptions to this ofc, but still think that this shouldn't pump toughness. +5/+0 I could get behind, or +4/+0 if you want to be on the safe side.

Yea, I think +5/+0 feels perfect. It makes it a little analogous to red cards that do 5 damage for 2 mana with an additional sac cost, except this adds it to a creature's power until end of turn with trample, without an extra cost.

"Isn't this a bit OP at this mana cost and as a common though? Even without the Discovery part. +5/+3 for 2 mana is a lot."

­Phytoburst, Titanic Growth

"Red doesn't usually pump toughness, and when it does its only like +1 or +2. Few exceptions to this ofc, but still think that this shouldn't pump toughness. +5/+0 I could get behind, or +4/+0 if you want to be on the safe side."

Again, Phytoburst and Titanic Growth are the power comparisons. My preferred alternative if this doesn't work out would for +4/+2.

The comparisons are to green cards though. If you insist on it adding to toughness, +4/+2 would be a compromise.

Those cards are both green for a reason. Red just doesnt get those type of effects normally, they get stuff like Fists of the Anvil and Brute Strength. If it pumps toughness it rarely goes above +x/+1. I understand the thought process behind it but its not red.

­Built to Smash and Distemper of the Blood suggest this is within reasonable boundaries for red. Maybe this could be +5/+2?

Yeah I can get behind that. +x/+3 just feels too green to me. I usually associate red with pumping toughness from between 0 to 2.