Also called ZX, the Leo is a graphics card produced by Sun Microsystems in the mid-1990s. It was one of their first 3D graphics cards, and was the first one to actually fit entirely inside the case. (The earlier system, the Graphics Tower, was actually a large deskside tower, as big as the rest of the computer!). The ZX was a double-width SBus card which actually consisted of two cards sandwiched together. It not only took up two slots due to its width, but also had two SBus connectors in order to get enough power. The card was infamous for its power consumption, heat dissipation and relatively weak performance. It did provide hardware-accelerated 3D graphics, but in such a klugy, inelegant way that few people actually wanted it. A faster, but even more power-hungry version, called Turbo ZX, came out a bit later. The TZX needed not only two power connecters, but also a double-wide fan card to keep it cool. Although both the ZX and Turbo ZX were reasonably quick for 3D in their day, their 2D performance was nothing short of abysmal, almost unusable as a console and only somewhat better with X running.
The Leo is only supported between Solaris 2.3 and 2.6. It is possible to convince the Solaris 2.6 drivers to work on 7, 8 and 9, but only in 32-bit mode, which means that you cannot use a ZX in an Ultra 1 or Ultra 2 under later than Solaris 2.6. (Not that you'd want to, anyway - the UPA graphics options available for these machines are far and away superior.) Linux and BSD users are in some amount of luck, however. Both Linux and OpenBSD support hardware 2D acceleration on this card. Alas, the 3D features aren't supported at all, due to lack of programming documentation.