A free spell and extra tokens from there on out is a good deal for a deck wanting to go wide
Madison Li Energy Vortex Glint-Sleeve Siphoner Gonti's Machinations Guide of Souls HELIOS One Localized Destruction Phyrexian Ironworks Razorfield Ripper Roil Cartographer Saheeli, Radiant Creator Shielded Aether Thief Spontaneous Artist Stone Idol Generator
Rikku also comes with an activated ability that lets you Steal opposing counters, and her ability to make a creature that gains a counter unblockable for a turn works very nicely alongside Tiduss proliferate trigger
Prevent all damage that would be dealt to and dealt by that permanent until your next turn
These cards are effectively the same in terms of gameplay effect - although they may have different artwork - and are used to pay for other cards, activate effects and boost the power of your characters and leader during attacks
Eirdu, Carrier of Dawn is at worst a Baneslayer Angel of sorts, so everything Isilu, Carrier of Twilight brings is extra