Rather than an expensive ultimate you'll never get to use, Elspeth has three cheap and useful abilities
This only needs to make a single mana a turn to have similar value to a Llanowar Elves, which is a fine floor when you consider the cards ceiling of an extra 3 or 4 mana a turn

Sort Card Type Shroomish #69Common $0.55 Shroomish #78Common $1.36 Shroomish #72Common $1.70 Shroomish #63Common $0.90 Shroomish #108Common $0.35 Shroomish #127Common $5.74 Shroomish #6Common $0.23 Shroomish #15Common $0.27 Shroomish #RC2Common $4.40 Shroomish #4Common $0.20 Shroomish #5Common $0.18 Shroomish #4Common $0.05 Shroomish #3Common $0.15 Shroomish #3Common $0.13 Shroomish #6Common $0.07 Shroomish #5Common $0.12 Shroomish #2Common $0.08 Shroomish #6Common $0.07 Shroomish #3Common $0.27 Shroomish #4Common $0.21 Shroomish #4Common $0.31 Shroomish #5Common $1.00 Shroomish #2Common $14.69 Shroomish #7Common Shroomish #6Common $0.49 Shroomish #2Common $14.69 Shroomish #127Common $5.74 Shroomish #RC2Common $4.40 Shroomish #72Common $1.70 Shroomish #78Common $1.36 Shroomish #5Common $1.00 Shroomish #63Common $0.90 Shroomish #69Common $0.55 Shroomish #6Common $0.49 Shroomish #108Common $0.35

The Celebrations set features reprints of classic cards - so for me, the holy grails are the reprints of Charizard, Blastoise, and Venusaur, looking exactly as they did back in their nineties Base Set configuration, just with an extra 25th anniversary slapped on top
However, with Tearlaments Kitkallos still currently legal in Master Duel , players can run the Ishizu-Tear deck at (almost) full power for an enjoyable and interactive Yu-Gi-Oh