A little like a primitive Raikou- EX , actually
During damage calculation, if a player would take battle damage: You can make neither player take any battle damage from that battle, and if you do, send 1 Level 4 or lower Insect monster from your Deck to the GY, then, if you sent a Normal Monster this way, you can Special Summon any number of monsters with the same name as that monster, from your hand, Deck, and/or GY
Theres not much to talk about Llanowar Elves, but its potential for giving you a huge advantage in a game is huge
All this said, this should really only be seen as a jumping-off point for those who have been out of the loop for some time and folks who are just now deciding to start playing the game