If a Level 7 or lower "Red-Eyes" monster(s) you control, except "Red-Eyes B. Chick", is destroyed by your opponent's attack or card effect and sent to your Graveyard: You can Special Summon this card from your hand in Defense Position, and if you do, Special Summon as many of those destroyed monsters as possible in the same battle position they were in when destroyed. You can Tribute this card; you can Normal Summon 1 "Red-Eyes" monster during your Main Phase this turn, except "Red-Eyes B. Chick", in addition to your Normal Summon/Set. (You can only gain this effect once per turn.)
Cannot control battle position revived monster is summoned in.
Must tribute himself to gain additional summon.
Here are some of the Monsters that can trigger the Special Summoning condition of Red-Eyes Retro Dragon.
Red-Eyes Slash Dragon is able to revive a Monster equipped to itself when he is destroyed. Combined with Red-Eyes Retro Dragon Special Summoning himself and reviving Red-Eyes Slash Dragon, this combo can quickly swarm your field.
When you tribute this card, you don't tribute summon using it as material to set it off. The "tribute" is a cost that you activate on the card. After that, you can Normal Summon another Red-Eyes monster assuming you have the tributes (lvl 5 or higher) or a free space on your board (lvl 4 or lower)
I wonder if they'll give this card an errata in DL considering "Red-Eyes B. Chick" no longer exist, even in DL.