When you discard an opponents card, you preemptively handle their threats or interactions
Thallid Devourer continues that trend by giving itself +1/+2 until the end of turn for each Saproling it can devour
All of that is for two mana as well, meaning you can do this every turn from turn three onwards - or even earlier if you can generate the mana for it
On Pokmon cards, it will appear to the lower-left of the Pokmon image while on Energy and Trainer cards it appears in the upper-right and lower-left corners of the cards, respectively: Now that we got that out of the way, lets go through the list
Either way, it looks like this card won't be viable in any other format except EDH
Maximizing Shaile, Dean of Radiance Creatures (31) 4 Stonecoil Serpent 4 Conclave Mentor 4 Swarm Shambler 4 Luminarch Aspirant 4 Clarion Spirit 4 Jaspera Sentinel 3 Shaile, Dean of Radiance 4 Star Pupil Lands (21) Spells (8) When it comes to maximizing Shaile herself, the card we want is Clarion Spirit