Like most Magic: The Gathering cards, the value of Soul-Guide Lantern depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Wilds of Eldraine)
You can check recent sold listings on eBay, use tools like Pokdata or TCGPlayer (for non-Aussie comps), or head into a local card shop like Cherry for a valuation
We can add photos of the reverse side if you are interested
As I alluded to before, the Thallids (named after the now defunct taxonomic group Thallophyta ) are fungal creatures created by the elves, which in turn create smaller creatures (which may just be their larval stage) called the Saprolings
Be careful of who you make deals with and who you give resources to, but also dont be afraid to give your opponent a little bit of help if it means you get much farther ahead
Luffy Alternate Art card is another of the market's current most expensive One Piece cards