They should be absolutely everywhere following the release of Lord of the Rings: Tales of Middle-earth, and, much like anything that gets reprinted in a Bonus Sheet, this will drive their value into the ground
This list focuses on cards that can put counters on themselves and others, with a bias towards Commander and Cube, though all-stars in other formats can show up
Just follow the instructions on the card
We tested the idea in the spring of 2020 in Ikoria: Lair of Behemoths with Godzilla Series Monster cards, which put Godzilla characters on cards from Ikoria: Lair of Behemoths
They can be fine in small doses, especially if they gain a lot of life, but they dont meaningfully impact the board or advance you game plan
(A spell is wordy if it has four or more lines of rules text.) 1R, T: Choose target creature you don't control