Spell or ability taps a creature and, very often, that permanent can't untap during its next untap This is an offshoot of the last category, and one that isn't quite as permanent an answer
If you do, add this card's abilities to that spell
If youre able to add counters to Conclave Mentor itself it also gains you a lot of life when it dies, which helps you stay alive and activate abilities that require you to pay life
Toss in some mana dorks that tap for mana equal to their power, like Mona Lisa, Science Geek and Gyre Sage, and you can storm your way up to a lethal Fireball
The graphic they added to the Mystery Booster packs had a square background, and the one they used for The List seems to have a rounded background, which creates a telltale difference in the shape of the cards border as you can see on Chatter of the Squirrel and Ancient Den as well as subtle changes in its placement on new border cards, as seen on Boros Challenger
Eventually, they used the skeleton as a shield for my strongest attacks until they pulled a card to decimate my creature field, opening me up to the final blow