While they were in the set as individual cards at vision design handoff, hearing so much support for them ensured their place in the set and inspired me to put them on the same card since they were so often talked about together
Finally, for five mana, it lets you shuffle your library and exile the top card, letting you play it without paying the cost
You can give an indestructible counter to a creature thats attacking, you can proliferate, and you can move level up counters around, so theres plenty of interesting stuff you could do with Tidus
Your high-cost characters are incredibly useful for protecting your board and closing out games, but with only seven cards that cost five or more, you might be better off keeping your inkwell small in some situations
However, you dont need to pay for it like that: Dismember allows you to pay for Phyrexian mana with 2 life for each Phyrexian mana, making a total of 4 life lost
You then gain 3 Lore, getting you closer to winning the game