When talking about best blue cards for tempo, nothing tops an extra turn at two mana a true icon of the color
Eshki is a bit awkward as there are only a few creatures with power 6 or more to get the most from her ability
When a card is put into your graveyard from anywhere, sacrifice Energy Field.
While a 1/1 might not be much to write home about, as soon as you get ten permanents in play and you get the City's Blessing, all your Saproling creatures get +2/+2 and suddenly become 3/3 threats
In the aggregate, the power level of the Flare cards are on par with the Force cycle
Invasion of Shandalar / Leyline Surge Invasion of Shandalars effect is a decent enough recursion spell, but if you manage to transform it (and keep Leyline Surge from being destroyed) you can cheat any one permanent in your hand onto the battlefield per turn, which can be absurdly good